Mom showed up this morning, good news she DID NOT put her hand down her daughters diaper.

Bad news her daughter is now putting her hand down her own diaper. so gross.
I check the diaper and its been clean each time. It doesn't look like she is scratching and I don't see and thing that could be ichy. I looks like she is just sticking her hand down and leaving it there. So gross. How do I make her stop, before I throw up? I wash her hand after i get it out of her diaper.