It's Not Really A Health Question But Hope You Can

It's not really a health question but hope you can help. I have a partner who has a 12 year old daughter. She wanders onto the bathroom when he's in the shower and when I said it was inappropriate she said oh that's ok I've seen dad naked heaps of times.
She also strokes his leg, arm, back and head and hugs him from behind which I think is totally inappropriate as well. He told me I'm sick in the head. There is no way I think anything sexual is going on but other people might if they knew or saw it