I can understand that you wanted to protect her somehow. From her point of view, the fact that you see the dress as an invitation to been rape by others is like saying that women has the fault for being raped, for dressing like that, therefore, if you see another woman dressed like that, you would rape her, because it's not your fault, it's hers, I hope you can understand what I mean. That's why she's so upset, because she should be able to wear what she wants and be safe. I hope you can think of this and relate to her a bit, it's also not your fault because this is something deeply learned in our society, and I assume of course you would never rape someone.