If A Woman Doesn't Wear Panties And Sits With Her Legs Open, What Happens?

That really depends on whether she's wearing pants or a skirt.

If a woman wore pants without underwear, it's unlikely that anybody else would notice.

Obviously, if a woman doesn't wear any underwear beneath a short skirt, and sits with her legs open, she's going to flash people.

I don't really see how you could get yourself in this situation by mistake (and if you did, surely you'd notice a breeze...) so it's likely that she's revealing herself intentionally.

I can't think why a girl would do this in public - pictures are likely to end up on the internet, and if nothing else, a lot of people are going to stare (and probably make lewd comments).

However, if your girlfriend is doing it around the house, she's probably trying to tease you. Maybe she wants you to have sex with her - although make sure this is the case before acting on it!