https://www.lightnovelworld.co/novel/isnt-being-a-wicked-woman-much-better-30071449. it's till chapter 200 something I guess. Completed novel you will have to look for the individual chapters at Tumblr
Mia is a complex character. She feels sorry for herself. She blames her family situation and is jealous of Debora for having a silver spoon. She is a pawn of the queen (who wants her son to be king/not the crown prince's mother).
So basically the queen is a devil worshiper and that's how she sacrifices people and gives Mia power to make her a saint who will support her son to become king. And Mia jumps like a bat from one person to another. But she fails everywhere. And she becomes so jealous that she also worships satan and lets him use her body as a vessel. Her horns comes out and later is defeated by Debora.
Small spoiler: Debora is the reincarnation of the Saint
I binged this entire thing all to ch 65 and it got more and more depressing with each ch I finished bc it’s SO DAMN GOOD AND ADDICTING. I was sad I was nearing the end of the latest released chapters. I love how she’s not unbearable, easy to love, and cheer on. Only note I have is the “revolutionary” business arc is lasting too long but I’m glad other plot lines like the lil brother is progressing. Also we haven’t even seen Rozzard, the big bro off in battle at all like when will he make an appearance?? It’s giving I will be milked for over 200 chapters lmao. Also I feel real bad for Mia like she’s getting abused and used. If she was an actual bitch I wouldn’t care but she’s so complex?? Her storyline is barely even touched too bc the business model arc is STILL in process ugh it’s gonna last forever since she said she’s gonna open multiple stores