She may have a urinary tract infection, and if she does, she will require antibiotics or other medications.
Urinary tract infections are fairly common. An all canned, or wet
diet may help if they are chronic.
If you cannot get her to the vet today because it is a weekend please get her to drink as much liquids as possible, any way possible. You can try giving her chicken, beef, vegetable, or fish broths, either on her food, or in separate bowls.