Am I wrong for wanting her to cover this hospital bill

I was having a meet up with a mom friend at her house. My 8 year old daughter was playing with our 9 year old daughter. I have a 10 year old autistic son who was also with him. There were a few other kids there but my son didn't want to play with them so he sat in the window. This is a two story house. Small house but still two story. I heard screaming and crying. Her 9 year old didn't understand why he was sitting at the window instead of hanging with the other kids so she decided to push him out the fucking window! He broke his arm in 3 different places from the fall. The other kids there also saw her push him because she thought he was being "stuck up" for not hanging out with them all. The daughter also admitted she pushed him. I spoke to my friend about wanting her to cover my the hospital bill. She believes she shouldn't have to my son was sitting in the window and should know that's dangerous. He didn't fall because he was sitting in the window. He fell because her daughter pushed him out. She said kids play and get hurt sometimes. I said once again. SHE PUSHED HIM OUT THE WINDOW!!! She doesn't believe she is responsible for this hospital bill because my son was sitting in the window. I said okay fine. We can go to court and let a judge decide who's responsible. She asked was I really about to drag her to court over this and told me since her daughter is so dangerous she's not allowed around my kids anymore. I am more than willing to go to court over this because I believe she should pay this hospital bill. Am I wrong?