Even

Navier tried to help her but she only shows her arrogant behaviour towards navier thinking that she have the upper hand because sovieshu favors her towards navier

Please she was a dumb slave that only saw worst in nobles bc she was a slave. If your parents are abusing you and you only see that, you will logical assume it's that way for everyone even if you are out of that place. She wanted his favor bc she didn't want to end up at the same place she was and I understand that(I wouldn't want that either, if I was in her place). She saw everything through the diffrent lance than Navier, some that looks so perfect in her eyes ofc she would think she has upper hand and tbh she has. Navier comes from the golden spoon household plus Diamond on bc she was promised crown since birth. We know it's not all sunshine and rainbows but try to explain that to the slave that thinks it's perfect life. You can try but everything will go over her head

Telling Rashta that Nobles like Navier aren't prefect is like telling a kid that thier time in the school is better than work

I'm sorry for answering so much but I'm trying to explain it in the way I see it and I came with new ideas how to explain it better I think.
I think it's natural for her to get greedy, even normal person, well atleast I hav same problem, while playing a game I got really powerful and cocky and I kinda abused that power.
People like Navier and other people that were born with that power and wealth are different breed bc they had responsible adults to tell them how to act and behave but a person like rashta that grow up as a slave didn't have that luxury. Since young she wanted that wealth and power(well atleast normal life) that noble had and when she got it, she lost herself with power and was too scared to lose it(funny enough she lost it bc of that) and there was no one to stop her. There was sovieshu but he didn't care about her, maids are lower class than her now and they can't say no. Other people around her used her for thier benefits so she didn't have anyone to correct her but like I said she got in the end what she dervered. She had sad upbringing but that's not excuse for ruining people's lifes

I think it's perfectly normal to try and sympathize with Rashta, in the beginning of the story I felt the same way as you (now I'm just jaded that the plot is so basic, fight me). She is a slave, someone who's looked down upon, from the very bottom of the hierarchy - that's a sympathetic position by itself.
Anyone would want an underdog to change for the better, it's just that this author chose her to be a rotten mut instead of taking the opportunity and write something with more nuance.

The thing is Rashta had opportunities to change around. Lots of people that had her back but we never saw any of it blossom since she never trust anyone and always unintentionally see herself as victim aka everyone is against her mindset mode. Where every criticism is misinterpreted as "they hate me that's why they say I'm doing bad thus their words are invalid." Navier altho unwilling tried a handful of time and begrudgingly tried to stop Rashta get accustomed in court but both Rashta and Sovieshu took that as Navier bullyng and undermining Rashta. Lots of warning she ignored... NO ONE managed to convince Rashta of othermise. Emperor is trash but he did offer her a hand and had her back but he was ignored (author should have thrown him under the bus too. The unresponsible douche. That let Rashta, a completely uneducated and ignorant of court matters, no offence intended, loose with the empress title and power.). Later on Rashta being an empress, her win over Navier and Duke Edgy support got over head and she straightout imitated the horrible people who treated her bad when she was a slave and thought she could deal with everything by herself.

Just like in irl, no matter how much you knock at someone's door to offer help, if it remains close there's nothing you can do.

I tot agree she's is a victim and tot innocent prior the story and when she was a slave. I also think she deserve all the affection and spoiling she received. Heck, I even admit and applaud her misdeeds if it's for her and her kid's survival sake. It's fair game imo. Everyone in this story is freaking sneaky with ulterior motives ready to throw everyone under the bus. BUT I cannot agree that she remains so when she ill intentionally took the initiative to harm others for entertainment. Or do it out of pure paranoia. Having an empress who kill and torture people bc of delusions and entertainment is terrible. Absolutely terrible. A menace to everyone. I actually also think it's fair that Gloriem was taken away from her bc I'm sorry but her paranoia and delusion is dangerous for her kid. . It just wouldn't make any sense to call her innocent.

Honestly I wouldn't get angry at the author or critized their writing. It's trash and dirty tactic but, it gets good result and the job done in terms of keeping the readers' engagement constant. Just think of the hateful Prince and Cersei from GoT or Reality shows that intentionally keep the most hated player till the finale. It's dirty but works. It's trashy but they did a great job writing Rashta as well even as a villain and scapegoat. She's a super gray character and her misdeeds are logical and make absolute sense in relation to both her background, ptsd/trauma (all its consequences), the circumstance and people she is surrounded. Written well enough that despite her horrible action people can sympathize.

If Rashta was written the way you wanted. Basically get the "villainess isekai treatment". Her story would be just any other underdog story of poor girl gets her justice and the happy ending she deserve. Which is fine and lovely but, objectively blatant, plain and unoriginal since the inflation of such trope in the webtoon and WebNovel. Not for good reasons but the way the author wrote Rashta allowed her to very unique and different from all the rivals we see often in webtoon romance stories with royals and noble girls.

Bruh... Navier helped her so much that she gave her husband away. I don't know what more you need from her.

Like I feel sorry for her since she was a slave a victim of the Eastern Empire slavery policy wich was absolutely trash and tyrannical. Like imaging finding out you are now a slave because a cousin you don't know or ever saw stole a pencil? It's pure injustice. I'm disgusted that a similar punishment logic (minus slavery) is still used in some countries irl.

It's pitiful that the happiest day of her life lasted a year. That she is left with the notion that her kids are all going to be slave like her bc of what she has done. She became what she hated her father for. She tasted freedom and lost asap and was told "hey you'll spend the rest of your life in this small dirty cell with your hallucinations and insanity".

But at the same time, I can't be delusional enough to say what she got is not a direct consequence of her predisposition, wrong choices and bad influences.

She maybe a terribly written character but never the less an interesting one that leaves the reader conflicting feelings of happiness bc justice triumph since she did harm lots of people but it's not a full happiness and joy due to her very sympathetic background. If this can comfort your anger as Rashta fan, imagine that after her death she is reincarnated or turned back time like all the villainess story or is living the happy and fullfilling life every human should have ^^

Tbh I think being a slave, and having no power then immediately being thrust into a position of power where everyone would essentially kiss the ground you walk on is what doomed her from the start. She wasn't born into that life and her mentality/thought process was never going to change so quickly especially after Navier left. I agree that it's normal to feel sorry for her, and part of the blame goes on shoeshoe or whatever the kings name is, because having a slave be queen was a problem from the start. Cutting her some slack from the start was a given due to her roots, but after some time when she had the chance to take the advice of those around her (aka Navier) and never did, it's only a matter of time till that pitifulness you feel for her goes away. But still, the blame lies with her and the king. That's just what I think though

*inhales*
I don't want the villainess isekai treatment, I simply expected her to be a bit more nuanced in character esp if she was meant to make it this long. A villain with layers instead of a vain person who in the end has nothing to say.
Sure, she doesn't have to be nuanced but if you're gonna stretch out a manhwa for this long, try adding some more points of interest at least. Before the main event, the divorce, I was pretty invested in the story and thought Rashta's villainy made sense. I saw the points you were making about her personality, BUT after that it just becomes this pathetic play where you're supposed to point and laugh at her downward spiral which is so boring. It's cathartic to see her lose this hard at first, but then the story keeps showing that again and again, and it's like we get it, so what now?
At that point even if she's a well-written asshole, her whole existence as a character boils down to this one bit where she just keeps taking the L so you can feel good for Navier.

GoT had much more going on than Cersei and her demon of a son, they were part of a greater net of characters and events much more complex than this manhwa. Here the story starts and ends with Navier and her problems who mainly are Sovieshu and Rashta - so why is it that Sovieshu can yearn, regret, be romantized in a way, and have nuance while Rashta burns like a witch? Sure, she deserved it, makes sense for her arc and so on but from a narrative pov it's disappointing, boring, at least it was for me.

It's ok to have that type of set-up and characters, but the god damn length of the whole thing is starting to make it more and more obvious that there's not much going on in the story department besides: 1. Navier good, happy end, 2. Rashta bad, bad end. If after 200 chapters the story boils down to this kind of black and white narrative, that's hella mid.
But that's just my opinion.

Disclaimer: I am in fact not defending Rashta and her actions, please shoot me for something else.