I dont think its just sasuke, in the begining people hated her because she just sat around doing nothing in all her battles. She only tied with ino because she has a split personality and ino only took over 1 part of her idenity. then in part 2, she was still all hell bent on getting sasuke back and was a bitch to sai.
and Sakura was also really rude to Lee in the beginign when he was so nice to her and agreed always to protect her.
But yes it also has ot do with the fact that whenever naruto tried to be nice to her or anythign she would just punch him or something and be like 'no i wanna be with sasuke'
So it originated with her being a whiny cry baby for Sasuke, but developed into just her entire attitude.