
I feel like amaryllis was set up well from the beginning to be a victimized pawn. She was definitely a bitch with an awful personality but I felt like it was made clear that her actions, while malicious, weren't done with a greater plan in mind. So there was only so far she could go as a villain herself when someone else was pulling the stings.
Her death was sudden but I'd blame the chapter limit the author was given more than anything.
I do really like how ashtarte thinks of amaryllis at the end tho, kind of acknowledging how while she was evil, she was definitely used. She was created to be used and thrown away.