Does she eat meat? Or other kinds of protein and healthy fat? Looking at what you've posted it looks about the same quantity of food that my 5 year old eats (she can polish off a whole one of those mini pizzas though) and she's only 25th centile in weight.
Breakfast: what about eggs and toast, or sausages (incl veggie sausages) and fruit, or peanut butter and banana wrap, greek yogurt with fruit and nuts and a bit of honey, hummus and pita, it doesn't have to be 'breakfast' food, just something with a bit more fat and protein.
Lunch: Any sort of sandwich or wrap with carrot sticks or cucumbers, or oatcakes and cheese with raw veg and fruit, soup with toast, pizza and salad, hummus and pita again with raw veg.
Any sort of fruit, yogurt, or crackers with cheese for snack
For dinner: what do you eat? I'm assuming you don't eat fish fingers. Baked fish with sweet potato chips (just slice them into wedges, toss in olive oil, bake for about 50 minutes) and peas, lentil soup with toast, chickpea curry, veg or beef lasagna with salad or a veg of her choosing that she likes, chunky stews and soups with toast, any sort of roasted meat if she'll eat it with a bit of mash and veg that she likes (carrots, peas, etc.), omelette or frittata or quiche. We also offer fruit for pudding after dinner, but mine rarely has it now as she fills up enough at snacktime and dinner, especially if she's already eaten plenty of fruit during the day.
I think I would focus on healthy fats (nut butter) and proteins of whatever sort she'll eat plus vegetables. That fills you up the most. Then just keep the crisps and biscuits and simple carb snacks out of the house except for a treat. We might have them at the weekend, but they aren't around day to day so makes it easier not to mindlessly snack.