Hey, Michelle, do you have a moment to chat with me? Cool. Thanks. I appreciate the fact that you like to flirt and the fact that you are good at it. However, when you flirt with me, it makes me uncomfortable. I'm asking you nicely to stop. I'd hate to get to where I'm ignoring you, because I think it's rude to do that, however, I will if you don't stop.
If "Michelle" (made up name for your friend) continues to flirt, just ignore the behavior. Sometimes people do stuff to cause a reaction in others. If you give her no response, hopefully she will become bored by your lack of response and move on to someone else.
