I have no idea if you're attractive or not, so I don't know. More likely, she's getting off not to you or your body specifically, but instead to the idea that you're getting off to her, because it's basically the forbidden fruit.
Suggest a strip game with her and see if she goes for it. Maybe something traditional where it's up to change who ends up naked, like strip poker. Or maybe something where it's more obvious that the intention is to get both of naked as quickly as possible, like rock paper scissors.
Reading your post actually gave me the courage to push my fantasies a bit further with my brothers today, and I decided to try walking around in just my thong, no bra this time. I wanted to see how they'd react. It wasn't long after doing that that I walked by one of their rooms and saw one of them jerking it furiously. He'd left the door just barely cracked, and part of me hopes that was on purpose in hopes that I'd catch him. I was very tempted to walk in still topless and let him stare while he finished but I chickened out. Maybe next time.
Is she with you now? Try complimenting her undies and see what happens. If she's not there, try texting her. Tell her you enjoyed her visit, say something nice about something that happened while she was over, and then mention that you know it might be non traditional to say but you just had to mention that she had very cute underwear today. See how she replies. If she bristles, the comment was reasonable enough, considering that she was walking around you in them. But if she's receptive, then you know the door is open to more, like perhaps having more sexually focused conversation when she's next visiting or hanging out nude around each other.
Screw it, this is making me so wet thinking about you living my fantasy. I've got to explore this more myself. Definitely spending more time topless around my brothers after this.
