Come on girl...you're smater than that to obsess with the OW...your H could have told her anything to start the A... he could have told her you were both getting D'd...he's more the problem than she is.
Let it go...you need to forgive...then move forward. If you keep her in your thoughts, you're just reinforcing all that is negative, not allowing you to heal. If you want to get mad with someone - be mad at your H...he's the one who strayed...the OW was probably told a horrific story about you and felt that your H was severing ties with you...
BUT...you know all this...don't you...you need to place the anger on the real culprit...your husband...not her...