(This is an old story I wrote three years ago during season 1)

Twilight Sparkle's birthday has come around, and Rainbow Dash is unimpressed with Rarity's present. When Applejack pokes a bit of fun with her friend, Rarity becomes unusually upset. Twilight Sparkle investigates her friend's feeling, learning something she never expected about her friend and why she is truly suited to be the element of Generosity.

Spanish translation: https://www.deviantart.com/spaniard-kiwi/art/Simply-Rarity-Spanish-translation-846034960