Well given that a whole bunch of posters on here (including me having read the posts) don't know what the outside hairy bits on a woman's crotch are called, it seems that some education might be in order, surely?
Little boys know their willy / penis and balls / testicles and girls have a host of euphamisms some of which are very strange and run the risk of not being understood by others, and a bunch of adult women posting on MN don't even have a bunch of easy, straightforward, understood terms at their grasp.
This feels wrong to me, like a bad thing.
So I would go with chunky's crotch (as it were) and then if they're getting anatomical then they need to get it right. Or pubic area as per errol would be fine too.
Thing is if DD came home and said this, it would conjure an image of hairy insides, as that to me is the vagina. I don't think it is common or widespread for most people to use "vagina" and mean the whole lot, many people say "bits" or "flower" or all sorts of things and for those people the vagina is, well, the vagina.
I think it's a real shame there aren't "friendly" names like willy and balls, that are commonly and widely understood and everyone knows what they mean.