Depends on Height. Height and weight go hand in hand. An average weight for a 5 foot girl is totally different than for a prebubertal 4 foot 5 inch child. Check with your doctor, and compare not age but weight for height.
Between 90-100 lbs. A 13 year girl who is 5'1" is around the 40th percentile for height. At this age somewhere between 90 and 100 lbs would put her around the 40-50 percentile for weight. The cdc and who have growth charts that can be helpful. http://medcalc.com/growth/ also ask your pediatrician to see your daughters growth chart at the next visit.