For God's sake don't do it!
The guys you are asking want to see women fucked by animals and rape little chi**ren. Will you really do like they say?
Never let get a hoe between you and your best friend.. NEVER!
This fucking cunt isn't worth it.. Fuck a hooker or a random hoe.
I don't want to give you the typical motherless answer, so just don't do it.
Maybe at some day they won't be together anymore, then you have enough time to fuck her, but for the moment, just no.
I was in the same position as you and as it came to the day on which they quit their relationship, I didn't even want to fuck this cunt anymore, it was just the the forbidden thing which turned me on in the end.
So think about it for real..