My son started puberty a bit early, just a little older than your daughter. We are going through some of the issues with it, so I'll tell you what I know.
The signs you are seeing may mean she's in puberty, but not necessarily. First, you need to go to your pediatrician to get a blood test, that will tell you if she is truly in puberty or not. If she isn't, you will probably just keep an eye on her. If she is, she will probably need to go to a pediatric endocrinologist..
The biggest risk for early puberty is stunted growth. It can cause them to miss growing years and/or stop growing too early. They keep track by taking an x-Ray of the child's arm for bone "age" and compare it to their chronological age. My son's "final" x-Ray showed that in 6 months he grew what he should had in a year, but his bone "aged" two years. This means he lost a year (about 2-3 inches) of growth in 6 months!
We opted to stop puberty until he can get a couple more years of growth.
Honestly, it's probably best to at least talk to her doctor and get the simple blood test for piece of mind. Our doctor told us they can have the hair growth a year or two before actual puberty, but the only way to know for sure is the blood test.
Hope this helps! If you need any more info, please feel free to message me.