IMHO is more about honouring your friend than trusting your W. My 5 cents...
Yes. Thanks. You said in 14 words what it basically took me three full paragraphs to say. But. Yeah. It's a matter of principle.
And, fwiw, my buddy has said "I got no problems with you hanging out with them if it comes to that", but, to me, that's not good enough. He still talks about that dude in derogatory terms, and still tells me how painful the situation still is to him at times. I dont think i could ever in good conscience get to the point of socializing with those two (W's bff and her AP) unless and until my own friend appeared completely good and at peace with them himself and, probably, willing and able to socialize with them himself. So, basically probably never.
H53/W51, R-ing 4/'18
"Do not arouse or awaken love until it so desires"-Sg.of Sg 2:7
"So oftentimes it happens,that we live our lives in chains, & we never even know we have the key"-Eagles III 1:3