Guys: So there's this certain girl...?

that you have feelings for, you guys have been friends for about 6 months now. shes funny, relatable, easygoing, cute, sexy, etc. but you are currently dating the girl's bestfriend at the time. your girlfriend is cool and everything but you're more interested in this other chick; but you fear being let down by the cooler girl and losing both women. how do you feel about this and what would YOU do about it??