The chapter in which Curley's wife is killed by Lennie contains most of the information needed to explain why the girl is responsible for her own death.
In the first place, she reveals why she has been acting so provocative around all the men on the ranch. They think she is sexually promiscuous and therefore dangerous because of her youth and her jealous husband. But she is not interested in sex and may very well still be a virgin. She is acting provocative because she is "movie crazy" and has dreams of becoming a movie star. She is trying out makeup, hair styles, clothes, and body language to see what sort of effect she can produce on men. They are just an audience, as far as she is concerned. She knows she has to be sexy if she is going to be a Hollywood movie star like Jean Harlow. She tells Lennie:
"Coulda been in the movies, an' had nice clothes--all them nice clothes like they wear. An' I coulda sat in them big hotels, an' had pitchers took of me. When they had them previews I coulda went to them, an' spoke in the radio, an' it wouldn'ta cost me a cent because I was in the pitcher. An' all them nice clothes like they wear. Because this guy says I was a natural."
In the second place, the girl is obviously very young, very inexperienced, and very naive. Otherwise she would never have stayed in the barn with Lennie and would certainly never have moved closer to him and invited him to feel her curly hair. She is too young to appeal to most of the men on the ranch, and too dangerous for them to want to have any intimacy with her. But Lennie is different, of course. He has a child's mind, but he is sexually mature and easily aroused without understanding his own impulses. Curley's wife should have had sense enough to understand what was happening to this retarded giant and tried to distract him somehow, so that she could get out of his grasp without struggling. Instead, she struggles and raises her voice. Men are playing horseshoes right outside the barn. Lennie becomes panicked.
"Please don't," he begged. "Oh! Please don't do that. George'll be mad."
She is so naive she doesn't realize that Lennie is sexually aroused. She is mainly concerned about keeping her little curls from being spoiled after spending so much time making them with a curling iron.
"Look out, now, you'll muss it." And then she cried angrily, "You stop it now, you'll mess it all up." She jerked her head sideways, and Lennie's fingers closed on her hair and hung on. "Let go," she cried. "You let go!"
She doesn't understand what is happening, and neither does Lennie. But the reader should understand that this is becoming a very dangerous situation, especially since George isn't around to separate them, as he was when Lennie got into a similar situation with a girl in Weed.
Curley's wife wants to be admired for her looks and sex-appeal. She invites Lennie to feel her soft hair because she considers it one of her best features. This is obviously a bad mistake. She brings about her own death because she is too young to realize that she can actually be sexually arousing and not merely look sexy on a movie screen. She does not understand the difference between fantasy and reality.