I think this may be her hymen and it is just the first time you have noticed. Most girls have one and it is normal. If it is not causing her further irritation then it should be fine. Good Luck
If you are concerned, take her to her pediatrician and have it looked at.
It's called a VAGINA, not virginia!
Maybe she's from the east coast, lol.
Sorry, yes, do take her to the pediatrician.