GF Shame

My friend's girlfriend is a total pig. Behind his back she sucks our dicks and let us fuck her all the time. It's hard to keep a straight face when I meet them knowing I've ridden the arse off her several times before. All the lads have had a go off her at one point or another, she only loves it. Two of our buddies spit roasted her in the pub toilets before. She once sucked a lad's cock and then went over to his house to fuck him. I'm not going to be the one to tell him either