She figures out how effed in the head he is pretty quickly, unfortunately he also figures out that she's the woman who died 16 years prior reincarnated, she keeps him at arms length but uses him to get proof on the queen and her actions and exonerate mc's name, eventually ruining the queen and causing her to lose her standing, douche king realizing she'll never be his, kills himself to leave a scar on her soul (pretty sure she doesn't care at this point but eh), queenie never learns from her actions and just to spite her kills herself just so the mc can't do it (again, the mc already got her revenge, so she doesn't care at this point.
Demon guy (forgot his name, claims her "soul", though this is a play on words, he basically proposed to her 16 years ago and they are bound together as lovers forever, so the mc get's a happy ending.