Yeah but the sister in law seduced the emperor when he was a minor (15 years old). She definitely is trash. If the queen was to get pregnant she will make her abort it without her knowing. That's more than Sus.
technically, fl isnt the other woman. she is the legal wife. whether he loves her or not doesnt change the fact that the FL is the one with legal rights of being the main girl
Historically, ppl married young (but that doesn't make it right). I agree the sis in law is an adult pine-ing after a child and will do some shitty things to get what she want. However, our girl wasn't technically legally his wife till after the fact they were an "item." The marriage was "forced" on him.
All in all, sister in law is trash and out girl can do better.
I currently don't hate the sister in law yet, because technically they aren't related. If the emperor really loves her and she reciprocates then technically our girl is the "other woman." If the story was spun the other way around, I think the reaction would be completely different. It is so interesting that authors can do that with stories.
However, I will say sister in law is sus, so I will probably hate her. Also, gotta support our sweet innocent girl, but emperor is trash XD