How do you know if she likes your friend?

[dipuc cupid]

Well, one of my best mates thinks of himself as a womanizer but he does get girls in his defence. Nearly every girl likes him.
My girlfriend claims that she's takin' the piss out of him when she says things ('cause she doesn't like him for whatever reason).

But what i've picked up on is that, they both do not like each other for what ever reason, my girlfriend tries to make out that her and her mates laugh at him an' whatnot, she always asks if i'm with him when me and her aren't together and one thing that damaged me but i haven't said to either of them is that when we were all out he was saying something to our group (her mates and our mates because we were all together an' we were decidin' where we were going), he said whatever he said but the way she looks at him... I don't know if i'm bein' paranoid or whatever but it just nags at me. Also, me and him went through a rough patch because of her an' she was sayin' he was a dick an' whatever but she was tryin' to make me still be friends with him sort of.

I'm confused, anyone help?