The inappropriate images are not pictures of themselves but pornographic images of others, they send it in the groupchat and the girl who is 14 years old sees all of it but she also engages in the activity and sends in pictures as well.
If the images are of adults, then possibly it's a case of contributing to the delinquency of a minor. Not sure if police or prosecutors will do much if it is an otherwise innocuous group chat that the 14 year old is voluntarily participating in. Obviously if the 14 year old were sending images of herself, or if the photos being shared were of other minors or schoolmates, things would be much different.
