Hi Erica,
I went through this with my daughter. She was around your daughter's age, or when she developed tenderness and what they call buds in her breasts. The pediatrician referred us to an Endocrinologists, and after an exam and blood work, it was found that she indeed had Precocious Puberty. We monitored her for some time, and around the age of 8, the Endocrinologist and I decided we would start her on meds (monthly Lupron injections), to suppress puberty. We kept her on the treatment for nearly a year. Her last blood work test before the Lupron injections, revealed that she was nearing the point where she would get her period. The doctor estimated it, as possibly 6 months. I thought this would not be good for my daughter to go through at such a young age, so I opted for treatment. The interesting thing is, after we took her off the treatment, she actually didn't get her period for a year or more later, even though the Endocrinologist had told me once you stop lupron injections, the hormones kick in to their previous levels almost right away. Sometimes I wonder what would have happened had I just let her go at nature's pace, but I did what I thought best at the time. I believe my daughter was around 11 when she got her period, which is considered normal these days. When I talk to her about all of this, she always tells me she's very glad she didn't have to deal with getting her period at age 8 or 9. I also had a talk with my daughter before deciding to treat, and even though she was just a child, she played a part in our decision.
I don't know if you've seen an Endocrinologist yet, but that is basically your first step. They will do a blood test to see what her hormone level is. It is a timed test. They insert a cateter, and draw blood about 3x. I believe it's hourly. I don't remember all the details, but it's something like that. We had to spend several hours at the doctor's office every time my daughter had the blood work drawn. It's a pain, but it's the only way they can really tell where your daughter is at in puberty.
Sometimes girls will get buds, and not actually be in puberty, so you don't necessarily have anything to worry about until you see an Endo. Once you know where you're at, you can decide what to do next. Most doctors will take a wait and watch approach at first. One thing my doctor told me early on is that weight & diet play a very important role. My daughter was always big for her age. Even as a baby. She always insisted my daughter watch what she eat, and eliminate as much sugar from her diet as possible.
I hope this has given you a little idea of what to expect. Any questions, please don't hesitate to ask
Good luck.