depends what she's snapping. if she isn't doing anything sexual then leave her alone. she has friends who are guys, and u should trust that she won't do anything, nor will she accept inappropriate behaviour from them.
if u don't trust that, then that's an issue u both need to discuss.
Depends. Is she sending them nudes? If yes, you definitely have a problem. If no, it may or may not be a problem. Do some more digging. But also don't be too nosey and untrusting. Bitches hate that these days.