take said arm. Hold out parallel to floor and in line with shoulder girdle.
Hold wrist in your hand. Twist sharply and wrench aswell. If she is still conscious then it may hurt. this will untrap the nerve.
Just in case you're a retard then don't do that. twas a joke.
It will be a nerve disorder clearly so go see a neurologist. The neurologist will then tell you to go to the physio if he thinks that will help.