Sure, but why are they not proud of being friendly?
Maybe they're just not that friendly
What does she have that you want and speculate she doesn't deserve?
Then just say that to her. What kinda jerk friend puts you in a position to compromise your morals? Maybe she can ruin her own life without your help for a while.
Unless she has good reason to fear for her safety, or something
So they having an affair?
It sounds to me like there are some underlying issues there.
That isn't friendship