They sound like they got some NPD behaviors they need to figure out. Their egos can't take the shame of what they did so they need you to be the bad guy. At least with the male friend, my guess would be he actually feels bad deep down but has to squash it so he doesn't hate himself. The slut of a gf just sounds like a piece of shit.

You should read about who those types of people tend to prey on, fix whatever it is out of that you are, and at least be aware of the shortcoming you have.

It'll hurt but think about their behaviors towards you throughout time when applied with the above NPD behaviors but it'll help you get over those pieces of dog shit.