You can't fix your image with everybody. Unless she's actually someone you consider a friend, I wouldn't bother.
Some people think I'm totally weird and awkward, and of course I have a stutter, but I've long decided that people are gonna be okay with it, or they aren't. I don't bother explaining my stutter unless I'm actually interacting with them and it's clear
right then that my stutter is making them uncomfortable. For some reason, people go, "Oh, okay" and relax when I tell them I have a stutter, even though it was really obvious a few seconds ago that I have a speech impediment.
I dunno whether they assume I have some kind of neurological problem first or...something.
Anyway, I wouldn't go out of my way to explain it unless you consider her a friend. If you'd joked, "I just want to practice with my camera!" just as someone looked at you funny or made a comment, that would work. But since she didn't even do that, she's just being just as creepy as she thinks you're being.