i agree with the above answers as to the possibility that it could be an infection or irritation, but they dont generally last that long without the child approaching the parent.
have you told her about 'the birds and the bees' yet? if not, maybe now would be a good time to gently broach the subject with her. ask her what she knows about those things, and correct her knowledge. if she has been molested, the person who did it may have threatened her or to hurt people she loves, so if it is abuse, she will be scared to speak about it.
also, if she has been abused, she might have been told its some type of game, or exercise or something, so ask her if anyone has ever touched her down there, and if she gets scared or defensive, let her know she is safe, and that talking about it will make the person go away and stop what they are doing, and nobody will be hurt.
its normal for girls that age to start being more independent, again, with the above statements, she could simply be discovering her body and finding out what feels nice and what doesnt. its quite normal for girls that age to explore, but they generally dont know that its a private thing.
the best thing to do is talk to her in a comfortable setting. be gentle because if she has been molested she will be very scared to talk about it. the one thing to remember is to continually reassure her that she is safe, and you will protect her. that will make it easier for her to open up about anything that may be bothering her, and it will also let her know that its safe to talk to you about awkward things when shes older.