Before I had a girlfriend, depending on which mate it was. We always put friendship over girls, meaning they were fair game
Eg. She makes a move on me, We're still best of buddies, no matter what I do. Kinda helping him out actually, separating the keepers from the non keepers (Cheaters from non cheaters) She makes a move on me, he finds out, he leaves her. Simple as that.
Remembering depending on which mate it was and how long they have been together etc. Some mates it's a lot more ... Normal, lol.
If she was single then it's your choice, I would do it if she was single even if they broke up like 2 days orso maybe she'll be the perfect match and I'd had to leave her alone because my "friend" was still crying about her blabla rubbish rubbish