What to do when another pua approaches your girl or your set?

[BlackEricNorthman]

That's probably not bad advice for a girl you just met. Only thing is, that line is so old it screams "PUA! Mystery!" louder than The Cube does.

Well you can paraphrase the line I used (I wouldn't really say it like that. I'd probably use quite a bit more swearing and flagrant use of the N word), the general idea with my approach would be to humor the guy but don't play into a "pissing contest" with him. You want to treat the invading male as a "comical diversion" rather than "an obstacle that needs to be dealt with".