I'm sorry but i wouldn't do it. you need to think about how you would feel if someone asked your girlfriend out?
Ask the girl.
ask her or get somone to ask her
You don't. >_>;;;
ask her
ask
"be ma boyfriend"
Ask your boyfriend. If you don't trust his answer he shouldn't be your boyfriend.
the smartest thing to do is ask.
If I was the girlfriend, and I know what's going on, I will talk to this girl and ask her what she is trying to do. I will ask her if she knows that the boy she is trying to flirt has a girlfriend. I will be civilize and calm and be professional about talking to the other girl. I will also tell her how will she feel if it was her boyfriend that's being flirt by another girl. Then I will ask nicely to stop flirting with my boyfriend.
You ask
The most appropriate way is simply to ask her.
Ask other people to ask that girl if she has a boyfriend. Just remind them not to mention that you wanted to know.