Honestly, I don't think it's that excessive. Maybe a little bit, but not overly.
My 2 big kids eat heaps through the day. Just today (and it's only 12.45) they have eaten, two slices of toast each, a muesli bar each, mandarin each, one banana, one bowl of chicken noodle soup, one tinned spaghetti toastie, a cup of milk each, two buttered arrowroot with sprinkles biscuits each. And the day is barely half over. It does slow down in the arvo, but generally they will eat more until 3.30pm when I stop feeding them in preparation to get them hungry for dinner at 5.15/30pm. Then they have dinner, and usually some fruit or yogurt (sometimes a treat like cake or icecream) after dinner.
But that is my kids, your kids are different and you know them. If you don't think your kids would eat that much, could you pack all of their own food, and then she won't have to feed them at all.