Ignore them and try to make new friends. They aren't worth your time or worries if that's how they're going to act. You obviously deserve better friends. People change and it's not always for the best but stay true to yourself dont change yourself just to stay friends with them and try not to worry too much just try to get out there and make new friends who will truly be there for you :)
If he's a good boyfriend he will ignore the Wh*re. But if he doesn't ignore her, trust me you'll find someone who you can trust and who will ignore her. Everything happens for a reason. And maybe this is happening so that you can see he is a good boyfriend, or that he isn't.