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.
My three year old daughter uses the bathroom more than 15 times a day or more. I have had her to the doctor and has had many test. But all the test came back normaly. The doctor told me she was not releaving her self fully. But I have went with her and she pees till she says she can't anymore. Within minutes she is having to pee again. We have even tried to cut her drinking fluids down and that still did not work. I need help. I have no idea what else to do. So will some one please send me in the right direction.