I quite like “The Princess of Alderaan” title, actually.
I like it too. It’s better than “A new hope”, a title that I find quite bland. But I think a better title would have to include a reference to the rebellion, as the other two titles in the trilogy reference the empire and the Jedi. With rebellion in the title you would have the 3 main organizations referenced in the trilogy titles.
What about “The Rebel Princess of Alderaan”? Or “The Rebel Princess”!