Bother with what? Initially their love for him was fine. Back then, Sasuke had a great personality and he saved Sakura and Karin's life a number of times. But ever since he tried to kill Sakura and stabbed Karin right through her chest, I cannot find any other good reasons why the two girls are still chasing him. Maybe they just want the old Sasuke back, but the things he did to them were horrible and no women would want to be with a man who attempted to kill her. However in the world of Naruto, that is obviously not the case.That is not why she is in love with Sasuke.
It's like some people don't even bother at times...