Mine isn't so much a flap as it looks like the thing that is in the back of your throat (I don't remember what that's called) but a little smaller. I always thought everyone had that, until I figured it was probably a piece of my broken hymen. At least that's what I figure it is! It's never really bothered me during sex as it hangs from the top of my vaginal opening, not the bottom. My gyno has never said anything about it either, so I figure it must be common!