Many kids are picky eaters.
As the age increases the growth decreases and hence the calorie intake also reduces.
You have not mentioned about her present weight.
But I can understand your worries.
Just be sure that you don`t give her more than 2 glasses of milk a day.
Cut short on all junk food- like chips, biscuits, chocolates etc.
Also do not give her lot of juices- which will not contribute to calories.
Whatever food she eats, fortify it with ghee/oil/ nuts/ cheese/ peanut butter etc. These are calorie dense foods. And offer her food in various interesting forms, shapes and colors. This will make food items interesting.
Make sure you give her plenty of fresh fruits and vegetables, dal, eggs daily.
Also consult your Pediatrician- who will be able to tell you the ideal weight and height for her age. You may also ask your Pediatrician for a micro-nutrient supplementation- because some kids with hidden micro-nutrient deficiencies do not grow well and have a poor appetite
Hope my answer helps you.
Wish your daughter good health.