Hello
First thing, she needs care and more positive parenting and second coming to study, it's always different in each individual..
No both children will have similar grasping power, so don't compare her and third about her academics and marks consult her teacher and ask the draw back or minus points in her study...
Next Steps
she need counselling...
consult a child psychologist for counselling to her...
Health Tips
if there is any major behavioural change consult children psychologist..if there are any physical disturbance than take medical advice with doctor..