Ok, she probably doesn't know what to say either. And as you care so much about her, it is normal for you to be confused as well.

However, it is really "important" that your wife doesn't think that by "telling" she has ruined anything or you have changed your feelings about her or your desire for her. As you know PTSD has that aspect of "low self worth" about it so you want to make sure you don't feed that feeling in anyway. Yes, it is a challenge to discuss intimacy because there is genuine uncertainty. But it is something you can work through.

Yes, you should sit with the therapist so you can get her guidence with this challenge.

Be patient, this will slowly heal.