My daughter is 13 an always wetting her bed what can I do?

DDAVP (desmopressin) and ... It appears your child has never achieved bladder control since birth (primary enuresis). Children with primary enuresis often respond well to ddavp(urine concentrating hormone). In case of poor response, alarm device attachable to underwear would be next treatment option which provides higher success rate. Consult your pediatrician for further details.
Nocturnal Enuresis. Bed wetting should be evaluated by medical provider in 13 yo. Behavior techniques can include limiting fluids before bedtime, counseling and bed-wetting alarms. Initial evaluation usually includes detailed history and exam, urinalysis/culture, and sometimes serum evaluation of kidney function. Also see: http://www.Mayoclinic.Com/health/bed-wetting/ds00611.