My friend's sister in panties

So as the title says, I have a question about a certain female behaviour.

I've been going over to my best friend's place for years now, and lately I've noticed his sister walking around their house in some kind of panties a lot of time. Basically, she walks around the house in something that is just a bit more than underwear, so at times it can be somewhat revealing. I can always see a part of her butt clearly, but what made me reconsider the whole thing and write this thread is something that happened 2 days ago.

She walked into my friends room and started talkin to the two of us (mostly to me, coz my friend was bussy at the moment). She was in some kind of panties, I guess, and as she rose up to go out of the room, I saw her vaginal lips (cameltoe - so to say) through those tight panties.

I know that many girls walk half-naked at home. I have a sister who does that when she's in her room or when she goes throught the house on her way to the bathroom. But she never does it when we have guests.

What I want to know is: is it possible that she is more than aware of what I could have seen through those tight panties? Is she not putting some more clothing on herself on purpose when I'm at their place, or is it possible that she is really just so casually that she did not even realise some of her privates are visible through those panties?

I have no idea what her intention is. She could be completely lacking in inhibition or she could be an exhibitionist. But it's rather odd that she hasn't figured out that clothes are kind of expected when guests are coming.

You could always ask your mate about it. "hey, what's with your sister wearing just undies?"

I believe she knows clothes are expected when there are guests, because she is never in her undies when, for example, they have their parents' friends come over. I'm not saying she's ALWAYS in her undies when I'm there, but sometimes she is, and this last time it revealed a bit more.

I think it doesn't matter.

Again, I suggest you ask your mate about it. I'm sure he'll tell her to cover up after you've had the conversation. Problem solved.

Are you older or younger then her, OP?