Is It Safe To Give Sertraline-Zoloft For Depression In A Child?

My 12 year old granddaughter has been depressed. The pediatrician has her on sertraline-Zoloft now. She showed me showed me her arm today and told me she cut it herself. She has been in the gifted program since grade 3-now in 6th grade. We have had a few stressors over the past 4 years- birth father has no contact, her uncle moved out of state, my husband of 30 years left us-we are now divorced. She and her mother lived with us...now the three of us live together, in a little rented house. She was depressed 3 years ago, had counseling and Zoloft for six months and became her old self again. She puts so much pressure on herself academically, has several good friends, girls and boys, basically from the gifted programs she s been in. She wants me to not tell her mother, but I feel it is necessary. Her mom, my daughter, is Bi-Polar and was diagnosed in the fall of her first year of college. I am a retired RN (Operating Room) and I know that she needs some more help. She also is taller than me, my son and dtr are both tall and she began her menses at age 10! Thank you for your time and efforts, Amy Ensminger. .