Sorry you have to go through this. Here is my 2 cents:
1) Only ask questions if you are ready for undesired answers. 2) Have you read "Not Just Friends"?
Knowing the truth is good, but the truth may hurt.
I doubt she will talk to you.
The only person I can control is me. I can control my thoughts, words and actions. I can set my boundaries. I can set my goals. I trust my feelings. I do things that were once unnatural but "the right thing to do".
My understanding that all cheater are liers. The cheating and lie is exciting and makes the A all that more attractive. You caught him once, now he may be sneakier.