Hi, Stress can be due to academic pressures, physical changes,peer pressure,etc . Social anxiety, phobia, learning problems,and being a bullying victim etc are some specific issues that you have to consider.You can talk to the school counselor and teachers.Be patience.You can also book an online counseling session though PRACTO.
Next Steps
Consult a psychiatrist if she has symptoms like, withdrawal, excessive crying, sleep disturbance,suisidal ideas etc,
Health Tips
Talk to her calmly, listen to her,and show love and patience.