This is my attempt to write a version of 'Rainbow Falls' that does not contradict past episodes and deals with the criticisms of the episode by various commenters.

Taking place before the qualifying trials for the Equestria Games, Dash is joining Fluttershy and Snowflake (sorry, I like that name better than Bulk Biceps) to help Fluttershy with her shyness.
Of course, the Wonderbolts want her on their team, so Dash has the same hard decision to make.