Some time hereditary factor may give obesity
She should go for thyroid
If she does not have thyroid then strict diet control is required.
total free fat diet.less carbohydrate
Avoid junk food,oily,fried and bulky fruits like banana,apple etc
Between two principle meal she should not eat any thing and if she gets hungry then take only green vegetables and salads.
Most important is physical exercise.go for running,jogging,swimming,rope jumping.