Hi dear for weight gain, you need to eat correct foods at correct time and quantity. Consuming high calorie and protein foods will help to increase. You can consult directly for detailed diet chart for her.

Hello..... Worm  infestation,  increased body  metabolic rate,  could  be the cause .Have high protein  containing  food.... Have egg, meat, fish, pulses, and foods cooked  using pufa (polyunsaturated  fatty  acid).. It's good for health.   Saturated  fat is not good for health..  Exercise  daily  in the morning..  It increases  your appetite .   Have more of fruits and vegetables....