There can be a number of problems that cause frequent urination. How long ago was she potty trained? Maybe she loves the novelty of being able to go by herself.
If she is drinking a lot during the day, then it makes sense that she would go often. If she is able to stay dry at night, that's a good sign.
As for possible medical conditions, you should take her to a physician for evaluation. It could be (and don't let this scare you) Diabetes Mellitus, a UTI, Pollakiuria or frequent daytime urination...which can go away without treatment, Diabetes Insipidus, too much fluid intake though not to be confused with diabetes, "voiding dysfunction" in which the child doesn't "go" all the way because they don't want to take the time to empty their bladders and want to get back to playing, vulvovaginitis for girls or meatitis or inflammation of the meatus or opening of the penis for boys.
I hope this helps. Check with your doctor.
