only you can decide whats right for you and what you need to know.
I read your profile story, and i can understand your pain and sympathize...the OW and her family were very dear friends of our family as well. I am truly so sorry for your pain. Its a horrific double betrayal.
While your WH may have given her an in, she contributed to the situation by pursuing him. Its like dangling a steak in front of a dog. she boosted his ego. because she was friends with you...and you probably confided some things in her...she saw a weakness....and she exploited it. Perhaps she talked to your WH about those things...fueled the fire. Gave him someone to confide in....was a shoulder to cry on. Once he responded, She went after him.
I often wondered what my WH and the OW talked about. We talked about it a couple times. I know there were a few things he confided in her that he shouldnt have. But he says he never bad mouthed me to her, and he never talked down about me. Its one of those things i will never know and i just have to take him at his word.
What it comes down to is...get the details you feel you need to help you move on. I will have to agree with you...he probably said whatever he needed to keep it going. I eventually just let it go. Such a hard place to be in. i understand. so sorry for your pain. hugs to you.