Dude you totally have to ask where she got those…..
Chinatown is my guess? But wow would be spend the time to look at those? Sorting for the right images and all that…
And Kenshin is not supposed to be there >.< I mean, sure he killed a lot of people but but but he is an honorable guy ( well at least I kinda see him like that)

Right.
I am SO gonna walk up to her and say, "Ma'am? You know those images you associate with witchraft and devilry and therefore displayed for Halloween to scare people? Can you tell me where you got them so that I may also partake of this satanic worship?" - which, of course, is not what I'll say, but this very easily could be what she'll hear.
Besides, what do I care where she got them? I know enough sources for these things already, you think she'll tell me something new? Probably off old tenants... Maybe a blood relative who's an anime fan... Can't say I care, really...
If anything, I better make sure she doesn't see the posters I already have - otherwise she might react to them in a same way you'd react if you walked into a room of a emo-goth-some-such who is fascinated with death and black magic. o_o
And yeah, I share your pain for Kenshin (I always for some reason thought he was a good guy), but this time I think I actually will let it slide. I'm sure Kenshin will forgive me.