You can add a higher-calorie snack at the end of the day, which will not interfere with your daughter's appetite for meals. You can use commercial liquid supplements with more than 200 calories, such as Boost, Ensure, Sustacal Plus and Enlive. Have your daughter increase her serving sizes by 25 percent. She will slowly get used to filling her stomach more. Add good fats, such as nuts, avocado, peanut butter and olive oil, because of the concentrated calories.
Sweets are good, particularly after a meal.
She needs adequate protein to build tissue, blood and muscle, so fish, chicken and meat will help. If you continue the vegetarian diet, be sure to include adequate protein and fat. Take this issue seriously. You need an aggressive plan worked out by a professional, based on your daughter's food likes and dislikes. Keeping a calorie count is also helpful.