Ok, knee injuries are an area of somewhat expertise for me (I'm not a doctor, I didn't stay in a Holiday Inn Express last night, BUT I have had two knee surgeries).
There's almost no way a doctor issued that brace. She threw that on herself. When I tore my ACL, the urgent care gave me a huge leg brace and the ortho basically said to toss it because it wasn't going to help. If it was so severe she couldn't move her knee without bracing it, she wouldn't be able to walk at all.
She could know she's torn something because there can be a popping noise when you tear a ligament. You can a