I would be asking the child to check her lunch bag and make sure that she didn't leave some of her lunch foods that she could be eating. Also it might have a lot to do with how much mom is packing for lunch and you may need to speak to mom saying child is still hungry and suggest she have more to eat at lunch since you provide snack only.

When my kids got home from school they were hungry and generally I would provide something like a peanut butter and jam sandwich as in two slices of bread plus filler or a grilled cheese sandwich and a glass of milk. Two homemade oatmeal chocolate chip cookies or a muffin and milk. Fruit it great but not filling enough so needs to be part of the meal. But at the same time the snack is a tide me over to going home and supper so while kids are hungry they need to be reminded of that and told any more food will spoil their appetite for supper. Make sure they have plenty to drink as that will curb some of the hunger.