I am not an expert or anything, but when I read this something sounded familiar, so I ran and grabbed one of my text books from college and found what I was looking for: "Hypersecretion of adrenal androgens and estrogen". I quote directly from the text..."in female children....may lead to early development of secondary sex characteristics." Now I'm not saying this is what your daughter has, she may just be developing extremely early but it is definitely worth a trip to the pediatrician just to be on the safe side. Best wishes!
Wow I have never heard of this before. I'm sure it's just a form of early development. Girls are known to reach pubity before girls. But six years old it a little young. I don't think it will cause any problems, but maybe you should take her to a pediatrician.
Maybe you should wait until somebody with a little more experience then myself posts an answers before deciding to take her to a doctor.