I actually think that he should've declined her.
A pure friend like that, just blabbing shit without thinking twice? It's obviously going to work out, but, c'mon man. Even if the guy is a huge whore, at least have some decency to not whore at your friends as well.
P.S: Before any of you @ me, the guy can fuck how much he wants, if I had an issue I'd stop reading. I just have an issue with him also indiscriminately having sex with his friends. That's like being a heavy weed smoker, and just nonchalantly inviting a non-smoker friend of yours to eat a giant weed cookie. You need to have some common sense, and separate things. Have a little sense of taste, and don't just throw yourself at everything that's offered to you.