I think you need to pop her along to the doctors...
By what you'll saying it sounds that a urine infections is more the probably cause, this can give very similar symptoms as the body tries to flush out the infection... But you do need to get her checked out and if you can get her on her potty to provide a urine sample before you go, the mores the better, as they can dip stick test this, rather than a finger stick test, with this the urine sample they be able to quickly decide if there's glucose in her urine indicating diabetes as a possible cause, or whether it's a urine infection causing problems...
But has I said, you do need to speak to a doctor to find out what's going on..