My method for dealing with the BF if he is calling me, stalking me, knows me, met me, or pestering me is to eject. If the BF thing is just a comment like
"I have a BF" (girls say this all the time who knows if it is true?)
ME "Girls ditch their BF's for me all the time"
ME "Well why don't we hang out first before you make your decision so quickly?"
But if she is like "My BF is here" or "this is my BF's B-day" I generally believe them and don't push it.
Besides girls have ditched their BF's for me at Clubs (harmless BF comments) and wanted to F-close me, hook up with me, and one time at a restraurant a girl ditched her BF just to try and talk to me. They didn't even leave together she wanted me to talk to her so bad! Just wouldn't stop staring. Never approached just a off night.