Some ideas for what she should be eating
Breakfast-
Eggs, these can be scrambled, boiled, poached or made into omlette. If short on time hard boil a load and keep them in the fridge can be used for breakfast or snacks.
Porridge with a spoon of peanut butter or fruit.
Plain Greek or normal yogurt with fruit and some walnuts or other nut.
Wholemeal toast with peanut butter
Savory muffins can be made easily and cam be batch cooked and stored in the fridge.
Overnight oats are great and really easy.
Lunch - if she is having school dinners you are limited by the choice that they have but if she is at home eg weekends or holidays then things like
Wholemeal bread sandwich with tuna, egg, cheese, humous, soft cheese etc.
Pitta toasted and cut into strips served with humous and veg batons.
A plate with cheese, veg, fruit, some oatcakes.
Soup.
Mini pizza made with a pitta bread.
Dinner
She needs good quality protein such as chicken, fish, lentils etc. Salmon is good as is mackerel.
Plenty of veg on the plate.
Jacket potato with tuna and salad.
Make chilli, curry, stir fry with loads of veg,
Snacks should be limited but some good ideas are
Oatcakes with cheese, peanut butter etc, cubes of cheese, yogurt, hard boiled eggs, a biscuit, fruit, veg sticks, humous
There is no reason not to have crisps, biscuits and chocolate but it shouldn't be every day.