Look the problem is that we disagree with the definition of cheating for starters, look this is what she said too him,
"Then she turns to me and says " Im going to have a dance... Im going to find a man and feel his ****! How does that make you feel?" I show no reaction so she says " aint you jellous... Im going give him a s***fy"."
My god read between the lines, personally I would have just played along with her and thought up something on the fly to reply to her with, chances are she wouldn't of ended up on the dance floor and instead I would be snogging my GF or taking her home, it's as simple as that, but it all depends on how she said it, and how she reacts to what I say to her, it's hard to judge 100% without actually being there, I don't plan things out, I just go with the flow, and in that instance I think I would have played the jealous BF that wants his baby.