This needs to be a hipster fanfic movie and all the ponies will be hipster Celestia starts liking Trixie and they fall deeply in love. Twilight is super-conflicted and almost kills Trixie in an epic magic battle.
>but before that
Twilight wants to break up Celestia and Trixie because Celestia belongs to Twilight because she is her faithful student, but while she tries to break them up, she should develop feelings for Trixie as well.
Twilight needs a way to vent her frustrations, so she joins a basketball team. Rarity is a cheerleader for the basketball team. At some point she should make out with Twilight because Twilight loves thoughtful bi fillies and dunt hate homoseckshuals. Rarity gets in a terrible accident and loses a leg or something. She goes to hospital, at which point she's supposed to ride home from the hospital in a taxi driven by Apple Bloom. She thinks Fluttershy is inside, but Fluttershy gets scared away by something. Sweetie Belle sees her chance and hides under a blanket in the taxi. Rarity confesses her feelings to who she thinks is fluttershy, and starts passionately making out with her/actuallySB. At a pivotal moment when thunder claps, Apple Bloom turns around, the blanket falls off of SB, and they all realize what's happening. Rarity and Sweetie Belle continue making out passionately while Applebloom is scarred for life.