I don't know if I would do that, Squiggle. I'd be more inclined to think that she would go off and fuck someone else because she thinks that her bf is back at home doing the same.

Like a majority of the above said, the fact that she loves to dance is perfectly normal. Most women do. Most women even love grinding. But she should be grinding on you and only you, IMO.

I think the fact that she told you that nothing had happened at the party when clearly something did is the bigger problem. Above anything else, you have to be able to trust your partner 100%. Until you have a calm conversation, there isn't 100% trust between the two of you.