I have an ex-girlfriend that is admitting herself into a mental treatment facility today. Can I use a temp guardianship doc?

Your question is not clear. For what purpose are you asking to use the temporary guardianship? When was it executed by the child's mother? It may not be considered valid if it was executed shortly before she admitted herself into a mental health facility as there may be a question of her competence to execute the document. In an emergency situation I would recommend that you find and call a guardianship attorney who can meet with you right away so that you can provide all the necessary information rather than seeking help on a forum such as this. Good luck.