I would just give her an honest answer and leave it at that.If she finds it interesting she will speak to you again if not PFFFT big deal.
I have a nosy neighbor across the street and they see me in both modes I don't hide who I am.
I have talked to lady and her husband over the years and I'm sure they think I'm gay because of the way I talk and dress.
What I'm sure freaks them out is when I kiss my GF on the front porch or when she gets in her car to head home.
Main thing is be yourself and don't act like they bother you.