I feel almost like Kate's deliberately just trying to do everything opposite of David.
- Kate wanted to get the fuck out of Richmond even though she got medical treatment there and her guts were spilling everywhere and near death. David wants her to stay.
- Kate now wants to help Richmond. David wants to leave.
a. Kate married David
b. Now she's hitting on her brother in law.
I think those cases correlate very well with her personality. She's a fickle, disloyal slut.