It seems to me that
1) It is good to understand that science hasn't proven anything about places we can't experiement on (including indirectly),
2) anyone who "believes" that the laws of nature might not apply elsewhere in the univese just doesn't understand what science is about. It is a useless question, as with pink unicorns, or green cheese. It is the same reasoning people use to *believe* in UFOs, ghosts, God, free-energy machines, and anything else where you can't prove the negative.
The semantics of "proven" is also slippery for this kind of person. Darwin's theory of evolution is not proven, for example. Regardless of whether she is a creationist, the problem is the same: she doesn't understand the concept of scientific proof, and if she has read as much as you've indicated, she is *refusing* to understand, and probably has read the various sensationalist physics authors (we have to contend with phd's with this same mindset :-( ).
Since we don't know for sure that there mightn't be a 12th dimension made of cheese, let's all sit around an think about how the moon really is made of green cheese after all, it's just that we only see the non-cheese 3D projection/extrusion.
If you don't understand Occam's razor, then you're going to believe whatever you want to. Science is about understanding what is testable, and then extrapolating with care.
It is one thing to have an open mind. It is another thing to take it to the extreme where "all things are possible", which is annoying new-age (and not just new-age, BTW) ideological position that is completely antithetical to science.
She believes that the laws of physics that we discovered aren't necessarily the same here as they are somewhere else in the universe. For example the properties of atoms of different elements. How would you prove or explain to a person like that these things are constant
She believes that just because humans have discovered something that works here on Earth it doesn't necessarily mean that it works the same somewhere else. I asked her what would lead her to believe that it would be any different somewhere else but she insisted that I had to prove to her first that it is constant to begin with.
A person like this might very well have an emotional investment in believing anything is possible, especially if s/he is religious. There might be no way to convince him/her because s/he will refuse to be convinced. Such people have a subtle non-distinction between hard reality and faith which cannot be penetrated. You'll have to figure out what sort of person you are talking to, and whether you want to bang your head against a brick wall.
Speaking of bricks... There is a test for such people. If she doesn't believe that the laws of nature are "constant", have her stand a distance away, and throw a brick at her head. If she ducks, then she should reconsider her disbelief about the "constancy" of physics.
Of course, there is another sort of person, the "contrarian", who will take such positions just to bait people. As with other such personality types, the question is "how much of my time do I want to waste" versus "will I have fun pressing the debate [with someone with a different logic/reality structure]". Your choice: be frustrated, have fun, or walk away.
(It appears that I'm annoyed by these "silly semantics" too

)