It takes a whole lot longer than 2-4 hours for milk to spoil. Milk is good out at room temperature for up to 7 or 8 hours - it just isn't cold - and we've gotten used to milk being "ice cold". It is perfectly safe for your daughter to drink the same milk in the morning that you put in her crib the evening before. However, you don't say how old your child is, but if she is a toddler, why is she still waking up at 3 am and drinking milk in the middle of the night? Remember that milk has sugar in it and can cause tooth decay. It is especially harmful if she falls asleep with the nipple in her mouth. Water, if she'll take it, would be an orally healthier option. But, remember that milk is pasturized, so much of any of the harmful bacteria, is removed before it hits your market shelf.