Consider yourself extremely lucky to have gotten the sleep you've gotten so far. Not everyone has been so lucky in the sleep department. :)
I think it's just a maturity issue as mentioned before. Eventually she'll grow out of it (quite possibly even before she potty trains), but until then I don't think there's anything you can do. It would be extremely cruel to limit her liquid intake especially given her age. The majority of "food" she should be getting should be either breast milk or formula until she's about a year. She's not really old enough to eat solids on a consistent basis anyway.
Good luck! Remember, this will all be over before a blink of an eye.