So I was in a night club and danced in a large group of people at the end of the party (it seemed they where having someones birthday party). There was a girl who I had maybe exchanged only a few lines.Then she comes at me and starts grinding against me but the weird part is at some moment she unbuttons my shirts third and fourth top buttons like in a way that I started to seem a bit gay (I mean I leave my two upper buttons always open). I closed them again and she said no open them. We struggled a bit and I won. Then she went away. So it was over in under a few minutes. This same thing happened at least one more time during that night.

So I am interested in your thoughts on why would she do that and how should have I reacted.
Now when I am thinking about it i believe I should have said that I will leave them opened while you are dancing with me.

It seems she was having a good time and when you were buttoning back your shirt you were ruining her mood... Like seeming a bit uptight or something... You should let her enjoy herself and take advantage of her openness, after all she started the whole bump'n'grind situation... Obviously she didn't like your reaction and she left...