Just a little things
You should know that there are some things that are not very acurate with the Frozen story. For example, how could it be 17 years? Elsa's coronation was when she was 21, that makes her being four years old when she met Smaug, and she doesn't look like that on the movie, she would be seven years old for me.
Read the story now
Also, I have the problem of the language, I can't understand everything because I'm spanish. But that's a problem for my own.
After all that, just let me say that your story is just AWESOME! X3 You really do a really incredible work with their personalities ( a psycho dragon and a sweet person) showing how different are they and also describing them in a great done way. Not to mention how the story catches the reader.
Really, keep going on this. You're doing great (just change that thing on the time-line).