wtb, it's terrifying and frustrating and probably seems unbelievable to all who don't inhabit the court system that visitation will go on indefinitely.
I have to echo lovemenow, though:
The physical evidence is that there are photos of the child on her iPod.
So the next question has to be Who took them?
You know and I know and the therapist knows who is the most likely culprit, but we can't arrest someone on likelihoods. We need some evidence and it will have to come from your child. When they say "no physical evidence", they mean no evidence of who took the photos.
CPS is the proper avenue for this. I know they're maddening and frustrating and terrible and I know you must just be about to jump out of your skin.
Just stay calm. Don't react at all. Be a safe place for your girls. That is the limit of your power for right now.
(((hugs)))