Copies works. I usually go with doppelgangers. Or just Mirrors once that's been explained.

[He shakes his head.]

I've met Mabel's and she's met mine. It's... usually impossible to meet your own, though you can talk to them by writing on the glass. It was... she was... wrong.

[There's more than a little revulsion on his face even just thinking about it. He knows Mabel as well as he knows himself, maybe even better. Seeing her but not her was... something he hopes he doesn't have to do again.]