Abrielle might act impulsive and weak but she was doing the best she could. This world was turning into a mystery to her and she wondered if this was her book, it seemed familiar but was still different in a way.
The more she stayed with him, the more she realized how much of a challenge it might be to achieve her goal. Honestly, she did consider just being a good wife and hoping Cedric doesn't kill her but that would not work.
It was uncertain how much the plot has control over the book and even if she didn't act like a villainess in the book as a means to escape her death there was no assurance her dear husband would not kill her. He was a psychopath. The story of a psychopath and a foolish noble lady that was obsessed with him.