Seriously, she just immediately accepts that they're from another dimension and totally understands what's up. You all understand what's up, right? Parallel universes and such? I'm not sure how to describe them, so I hope you are.
Well, I'll give it a shot. They're, um... Other universes? That are parallel to our own? Similar, but different? And stuff? And somehow things can be just slightly different in key ways even though cause and effect means changing one small thing in history can change a whole mess of other things, so it's sort of weird that parallel universes could be so similar? I mean, even allowing for every possible outcome, there's "possible", and then there's "the only way B could still happen if you changed A would be if you modified D, E, and F and rewrote certain laws of physics, and then a whole bunch of other things would change so it's not really possible to change A and keep B"? It's sorta weird?
Well, I hope that clears things up.