I do feel you are overreacting to the fact that she was dancing with some dude. And the grind is really no big deal. Heck, I was at a good friends birthday party the other night and his mother was giving me the bump and grind.

The part that I feel you are righteously upset about is the fact that she told you she wouldn't and then lied to you about it. Trust is one of the biggest thing in a relationship (especially in a long distance one). This is what I feel you should concentrate on.

Best of luck,

CCF