Turnabout is fair play

I’m in the greater Calgary area now. My sister came into town at 3:45 this morning, and considering that we live an hour away from the airport, it was a major undertaking to pick her up. But now she is here. Good times will be had.
We’re in the middle of nowhere, so my usually goal of exhausting her won’t be easily accomplished. Nobody is around here.
Usually when we are out and about and meeting people, I will explicitly introduce her as my sister. It might be rude, but if there is a pretty girl involved, I don’t want her to thing that I am unavailable. Not that anything is likely to happen anyway.
Interestingly, yesterday while I was in the elevator, there was the cute girl that lives in my building. I thought she was with her boyfriend, but she explicitly introduced him as her little brother…
Is she doing the same thing that I do? Is she available and finds me interesting? I’ve got to get on the ball here.