Lennie sees his attack as unintentional from the start, but upon finishing the job, he realizes that he "done a bad thing." Throughout the attack, his point of view was that he was trying to play defense. He knew he wasn't supposed to be with her in the first place (and he warned her). He thought he was settling her down and keeping her quiet. She thought he was intentionally hurting her.
Curley's wife likely sees his attack as possibly leading to a molesting-type of situation. She allowed him to touch her hair and it started out pleasant enough, but as a woman, she could have clearly read his behavior as if he was getting a rise out of this and turned violent to take it further. She grew angry.
well lennie was "mentally challenged". which explains everything you ... nimrod!
and curley's wife was a tart. the end.