I actually assumed it was a general consensus that grinding on other people is cheating, until I was talking to a girl and it came up somehow and she said that she wouldn't consider it cheating and does it on a pretty regular basis. That was pretty much the beginning of the end between me and her. It is basically simulating sex and the idea that it's how you're supposed to dance is just bullshit, as far as I'm concerned. I would definitely consider it cheating but what's done is done. Since she knows how you feel about it, you need to decide if you forgive her and she needs to decide if she cares enough about you to stop dancing that way with other people (despite what she may believe, there are other ways to dance, and I personally wouldn't even consider that to be dancing, in the first place). If she keeps doing it, even knowing what she knows now, it shows a great deal of disrespect for you and disregard for your feelings