I have a little DD who drinks heaps and heaps of water too, probably not as much as your DD but then again I dont really measure it as such, she always has a cup which i refill during the day for her and I drink stacks of water and pretty much everytime I get a drink she shares mine. My DD has been very irritable (which could be anything) she has not really gained weight since before 12 months but I dont think she has lost any, however I had her tested for diabetes last week and we get the test results tomorrow. My DD also sometimes gets a funny smelling breath which I have heard can also be a sign but again can also be other factors.

I really believe you should have her tested, its better to be safe than sorry, I dont want to scare you but Type 1 diabetes can turn bad very quickly and little ones can end up very sick. Most cases are not diagnosed in kids until they are very ill and taken to hospital. Get her tested.

Good Luck xoxox