If you have not seen an increase in the amount of water that she is drinking, then she may have a urinary tract infection. With UTI's the dog will experience a great deal of inflammation within the urinary bladder. As a result, even when a small amount of urine enters the bladder, it spasms and she feels the need to urinate.
Dogs with urinary tract infections typically urinate frequently, usually small amounts (not their usual). They may appear to strain after urination, there may be blood in the urine, and they may lick excessively at the vulva. Dogs with UTI's also often have accidents in the house because it's difficult/ too painful to hold it long enough to ask to go out.
I'd recommend bringing a urine sample to your vet for urinalysis. The easiest way to do this is leash walk her. When she squats to pee, put a soup ladle or other shallow container in the urine stream. Transfer it to a clean, dry container (avoid pill vials or containers that contained sugar as this skews test results) and stick it in the fridge until you can get it to your vet. It's best if they get it within 24 hours of voiding.
If she has a urinary tract infection, your vet will start her on antibiotics. They usually show improvement in clinical signs after just a few doses.