Right but, do I follow up with her about it?

I think my MIL's hope is that once she gets into counseling, it will be another person telling her she needs to absolutely cut off the A (if she hasn't already), and someone that will also be meeting her on the side to discuss her individual issues. I am very hesitant to enter into counseling w/o her stating the affair is over etc but not sure I see another way forward.