Maybe because it's possible to be friends with people without wanting to date/have sex with them.
It would be a wise decision not to "hit on" her at all since she already has a boyfriend. A better choice would be to find a girl who does not have a boyfriend and ask her out on a date.
Treat her better than her boyfriend does.
You can't.
If you are a girl, I would probably not mention it. If you are a boy, he probably already knows.
Just because people are flirting on the Internet and they are already going with someone it is cheating. Your boyfriend has no right to be in touch with this girl. If you are wise you would confront him about this and let him know you accidentally saw the text and read it and you are not putting up with it. Ask him how he would like you doing the same to him.
That's NOT Cool man.
Tell you her your feelings about her
just by being your self
There is nothing you can do if he has a girlfriend.Before making a move on him you should consider how you would feel if a girl did that to your boyfriend.
You don't! I am a girl and my boyfriend just went for the kill! I loved it!
just a friend
wait until she breaks up with her boyfriend and then make your move