I appreciate her ingenuity and care for the poor mosquitoes, but would mosquitoes be interested in blood candy? They find our veins by sensing heat, don't they? So the blood candies would have to be kept relatively warm for them to work.
And on a larger scale, you want to kill them since they're the mothers who suck the blood and they make the babies which just means more mosquitoes. Maybe you could get a bee colony? Bees are friendly and good creatures and your daughter would probably think they're sort of cute.