Ahhh, I'm sorry. I've got the same deal with this being my first year not trick-or-treating because I'm in college, so I feel you.
As for advice, I'm not great at that stuff, but I don't think it'll hurt to be direct unless she's actually aphobic, in which case I'm very sorry.
I told my boyfriend that I'm ace-spec, and he just doesn't get it and sees it as him not being good enough for me (in which case no one's good enough for me because I don't like anyone else!), but whatever. It's not fair. He's bi, and I could not care less that he feels some attraction towards men. Yet when I'm demisexual, his only response is, "so you don't think I'm hot?" And I know he was sort of joking, but I want to be taken seriously. Ughhh he's an amazing person, but this is the one thing that frustrates me.