Well what a slut. But I think its fine to 1.tell her she is a slut 2. tell her "get the fvck away from me.
But he shouldn't be having such a temper tantrum about it or doing things to get revenge. He should tell her what the thinks and dump her then walk away because that's what would be healthy for him.
You should never make a huge deal over this type of thing. It's one thing to feel this way and vent or somthing, but you shouldnt be showing her or others (with the exception of a very close friend) how you feel. But defiantly feel your feelings.
What a slvt.