Fluttershy should just forget about it -- it was years ago, after all, and Rainbow Dash really didn't do anything. And with how much good she's done for her... all it is now, should be, is a memory. A silly, insignificant memory. Not hurtful at all, when taking everything else into consideration. Even if Dash never apologized, having just forgotten it ever happened, it shouldn't matter to her.

Right?

A personal piece.