What a fun idea that the dinosaurs were dragons, @steph- your mother raised a good debate! 
It’s true that our perceptions of them continue to change (there’s an article here: Dinosaurs: how our understanding of what they looked like keeps changing) as science develops and they uncover more and more about the past.
When looking at the skull of a Dracorex hogwartsia (yes that’s the real name 
) it does look like a dragon!
[Pic from Chasmosaurs: The Dragon King Dracorex hogwartsia]
And there are certainly creatures that still live today that look like dragons- Bearded Dragons, of course, but even things like Glaucus Atlanticus 
It seems like your mother could be on to something, Steph!