I have hard time believing that she never behaved in that manner until now. You likely saw some other signs

Does she have any diagnosis? Not here to diagnose people but she sounds like a few people I unfortunately happened to know.

If your child is a minor, he belongs with his parents and she can’t say he’s not allowed in the house. Even if he was badly behaved, he belongs in your home. She on the other hand may need to start packing her stuff