I appreciate your concern!
Obesity in kids is definitely bad and to be avoided from the beginning!
You give her fat free skimmed milk,yoghurt and dairy products that are fat free.
Use minimum oil and avoid ghee or butter in cooking.
Give her more of proteins
and less of starch.
Give her salads and grated carrot,cucumber,etc.
Keep a weight chart and follow monthly.
Reward her for not gaining weight!
Good she has lot of activities.
All the best