What would you do?

I would comfront them and find out what their problem is. And find out if its really true that they were talking about me.

my best friend is my GF..........!!!!!

i would ask them why

If someone you know is talking behind your back, then would not be your best friend. Good friends are people who are loyal, trustworthy, honest and reliable so if they have anything to say about you, then they should say it directly to you and not to others. If someone talked behind my back, I would not call them a friend at all but I would make sure they knew that I had heard what they had said about me and what it had done to what had once been a good friendship, i.e. they destroyed it by their actions and/or words.

my best friend is my GF..........!!!!!