After spilling her tea, Fluttershy spills her guts as to how she knows so confidently Rainbow Dash is into colts through a first hoof experience under covers.

Allot happens in trade school dorms. Especially with Rainbow Dash as a roommate.

This is a first person story from Fluttershy's perspective as she reflects on a past event to Twilight after an awkward conversation. However, even though she tells Twilight the truth, its not exactly the whole truth.