My mother who is 72, has a left eye swollen and part of her left mouth numb what may she have. My mother got the syntoms when she went outside during the night three days ago and I don't know if she got bitten by a mosguito or something else.

See a doctor. Left face symptoms could be a stroke, nerve problem, infection or other problem. See a doctor if this does not resolve promptly.
If . If the skin feels warm to touch with or without mild fever she should be evaluted to have cellulitis ruled out. She may need an anti-biotic. If you notice any drooping of the eyelid, slight drooling around the mouth she should be evaluted to have bell'spalsy or seventh-nerve palsy ruled out.