I just rewatched the eppy and discovered something new and interesting (for myself) in the scene where Kate has come to Sawyer last night and now wakes up next to him, she actually starts kissing him at first, then Sawyer comments on how they didn't go all the way last night, but all in all the scene seems quite nice until - Sawyer brings Kate's hands over her head half-way and holds them down. At that moment, she pretty much finally asks him to stop.

I think it might have to do with her past, the way Wayne treated her mother, and I believe she got scared, she didn't want this to happen to her and that's (along with what Sawyer said when he found out she wasn't pregnant) the reason she decided to leave.

my opinion is that she likes sawyer, really likes him, but i think when he started going for it, she didn't want to. maybe to her, when they spent the night sleeping in each others arms, it was her "goodbye". i really think that she made up her mind before she even went to otherton about jack. i do not agree that how she handled it all was right. she shouldn't have laid in bed with him all night and then started kissing him in the morning. he had a right to be mad. but their argument is a window into their relationship;).