Heather really overreacted about Oz "making fun of her"

To me it was no big deal what he did, talked about liking the sweaters she wore and Stiffler was just being an obnoxious friend giving him a hard time like guys do and he just kinda laughed and slapped his hand. What exactly was the big deal? She got extremely pissed, didn't wanna go to prom with him and acted as if she caught him cheating with 2 girls or something. Does she not know how guys act with one another sometimes? she acted appalled over nothing.

Oz slapping Stiffler's hand was like the final straw for her, he was obviously not into what Stiffler was doing, he just kinda went along with him and briefly laughed like "Yeah yeah alright" and slapped his hand, i don't get what got her so upset. And nowhere did i see him making fun of her really.