The FMC took in poor, uneducated Tyrael that lived on the street, raised her like an helicopter parent without teaching her how to fend for herself, bringing her along into high society like a pet, grooming her for her "purpose" of being "the heroine", while showing how she didn't want anything to do with her own fiance. Then the bastard fiance manipulate Tyrael because of the FMC, and ditch her when it doesn't work. So now, Tyrael is alone, without any support, family, robbed by the FMC of what should have been a better life. And the FMC even stole the prince from her. The "revenge affair" was supposedly to bring them back together since Tyrael would lift the curse, but that quickly forgotten.
In normal (good?) "villainess in a novel" stories, the heroine either is a bitch from the start contrary to her portrayal in the "novel" and is the one ending up ruined, or is as good as she's portrayed and the "villainess" truly befriends or help her until the end.
Here, the heroine was good, and only ends up as a forced "antagonist" through the FMC interferences, and selfishness. I feel way more sorry for Tyrael than for the rich, noble, loved by the prince, FMC.