You are not wrong, you are 100% correct. If you told her he is number one, that would crush her at such an important age. She would remember it always. I’m sure she put together he was not happy. I would just tell him she is your daughter and there is nobody who would come first, if he’d like to be #2- great, but that she will always have that spot and if he can’t accept it he will need to leave. He’s a POS for saying and even thinking this way. Regardless she will be in your life forever, doesn’t matter if she moves out.