Starlight Glimmer: "You know how some ponies say nothing's wrong but you can tell something's definitely wrong?"
Twilight Sparkle: "……nooooooooooooo…..heh?"
This little exchange says worlds about Twilight Sparkle, Starlight Glimmer, and why the map chose Starlight to solve the Princess's friendship problem. Despite being the Princess of Friendship, Twilight is utterly tone-deaf when it comes to recognizing other ponies' feelings. Had the map sent her, it's unlikely Twilight would've even realized the Princesses were starting to have a falling-out. Starlight may be reckless, impulsive, and disregarding of other ponies' feelings, but at least she has a pretty good awareness of them.
not provided yet