Ya, her rejection of dark matter also confused me, becuse it’s not a theory but rather a set of images and observations. There are some theories about dark matter like MOND and WIMPs but dark matter itslef isn’t a theory that can be wrong, as unless our telescopes are just making up data, we can pretty clearly see that some galaxies have lots more gravity then they have things like stars and matter, while others nearly exactly fit the equations. While we still can’t say exactly what it is, hence the name, we can be pretty confident that we’re making maps of something.