How much are 13-year-old girls who are 5' 6 supposed to weigh?

There is a lot of variation at this age, since girls enter puberty and have growth spurts at different times. 13 year olds can weigh between 80 pounds and 140 pounds. The "average" is about 100 pounds, but the "average" height at age 13 is 5 foot 2.

Since you are taller than average, probably your weight will be more than average too. Also remember that it is normal to gain weight at this age, since you are still growing.