Is it overweight, underweight, or normal for a 12 year old, 5 foot tall female to be around 88 pounds?

Body mass index: BMI or body mass index can be calculated here: https://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmicalc.htm There is also a BMI calculator app. BMI in a 12 year old needs to be adjusted for AGE and therefore

Normal: The normal variation in weight at that height is about 79 to 111 lb. There is a lot of variation in kids that age as some hit puberty earlier than others and height increases often precede acquisition of muscle mass. This weight is well within the normal range.