That is completely incorrect. Rare to meet an HIV positive woman in the US wrong.
Due to the fact that you penetrating her, you had an exposure. The chances of her actually having HIV are close to zero according to the doctors on this forum. It's rare apparently to meet a HIV+ female in the US, but again, it isn't zero. I would be tested just to make sure but I would estimate that the chance you had gotten HIV from her, IF she even had it, which I doubt then is slim to none.
I base this since her status is unknown and since you know her personally the chances are even lower because you would of been aware of her sexually activity probably.