It all depends on how you want to appear. You could offer supplies, (and to me it seems like she is really trying to replicate your items,) and you never know, maybe offer a kit or something along those lines and maybe make a few extra bucks. Or you could simply tell her "I only sell pieces as a whole, I don't offer individual parts", unless maybe they are a returning customer needing to replace a piece. I myself would tell them you are sorry, but you can't sell the pieces individually. If she is asking where you buy your supplies, tell her a friend makes them or they are custom mde for you, if you don't want to share the info.