Is this a very sudden thing? (Has she always been outgoing and abruptly this happened). She could have a mild autism if this has happened gradually. My uncle had the same thing in his 40s because of a medication, which could also be the problem. If it is abruptly happening and she is having violent mood-swings, if she begins being very solitary, or if she starts dropping grades, I hate to say it, but it could be a demonic possession.