MC is a good idea as long as you feel she is working on repairing the marriage. If you sense she is just going through the motions to check the "we tried MC box" then its best to terminate the sessions.
During the, "I love you, but I need time apart" period we went to MC. During that series of visits, she vented about my past wrongs, and I had few opportunities to speak. When the MC gave advice that involved returning, she'd disagree or agree then change her mind after the session. When the MC gave advice about separating, she'd readily agree and adopt it. That MC was a useless experience from the purpose of R, and our eventual reconciliation came long after we stopped MC.
Our second round of MC was after she committed to the relationship again. We both talked and listened about problems we were each facing and tried to work towards common solutions.
The general advice is that MC is useful if and only if she's committed to the relationship. Is her focus on venting or getting to happy? Is a fair percentage of the session focused on what she's doing wrong and is she making changes to address those? Does she jump on advice that's pro-marriage or jump on advice that's anti-marriage? You're there. These are some factors to consider in whether continued MC would be more helpful or a waste of effort to harmful to your relationship.
If you have anger to work through about the affair, IC can help. Terms you set after her unfaithfulness should be about self-protection, trust, and respect--not a way to lash out in anger.
