I think many women, as well as some men, think that they can change the habits that they don't like about their mate and make them "a better person". The feeling that maybe if she loves him enough that he will start to feel the same for her when he appreciates all that she does for him.
The women friends I have who went through this had an inkling, no matter how slight, of them being played. They were rather sensitive to changes in their boyfriends' affections.