Long ago, following an age of gradual bitterness and hatred, the map of Equestria was divided in two parts: Solar Equestria, ruled by the Princess of the Sun; Lunar Equestria, ruled by the Princess of the Moon. Rarity Belle, living in Lunar Equestria, was but an aspiring seamstress who unexpectedly got summoned to the Royal Palace of Princess Luna --- all in a hunt for a priceless, mystic crystal near the borders of the rival country.
Things could only go well from there.

One fateful day, when Rarity seemingly died, all her friends retreated to isolating the (painful) memories of her from their minds. Sweetie Belle left Ponyville to live with her parents in Fillydelphia.
Applejack in particular found it much too hard to hear about Rarity and not break down. Apple Bloom, on the other hoof, wants her big sister to get over this loss and schedules the third Little Sister/Big Sister Annual Camping Trip for the betterment of her sister, Sweetie Belle and all her sisters' friends.
In account of the blizzards due for Ponyville and the surrounding regions, the CMCs and Applejack, Rainbow Dash, Fluttershy and Pinkie Pie head over to Ponway for the trip.

They expect many things in this land but a stone-hearted, frozen-eyed, half-wolf Rarity is certainly not one.

I sometimes feel like I hate myself.

I am… well, I certainly am not cocky. Heavens, no. Adequate manners for the lady with proper grace rebuff any such uncouth behaviour. A lady is never cocky. Self-important, proud, overconfident --- perhaps --- but cocky? Never.

Nevertheless, while ample words dignify a lady’s poise, the matter of how I treat those around me remains. All my life, long as I can remember, I have only ever wanted to be noticed. Growing up into a charming, young lady with exquisite taste in style and fashion, I longed to be mobbed around by fans, cheering out my name, as if I were a glamourous star.
My only true home was the spotlight.

And that thirst for the spotlight has, more than once, led to ruin for my friends. For Rainbow Dash, precisely. That day in Cloudsdale... ugh, the memories. Of course, everything turned alright in the end -- but I despise myself for it began in the first place.

Apple Bloom, Scootaloo, Sweetie Belle. The adorable Cutie Mark Crusaders. Younger sisters to the Elements of Honesty, the Element of Loyalty and the Element of Generosity.

They were so lovely, weren't they? Sure. But did they remain the same after five years?

Apple Bloom, Scootaloo, Sweetie Belle. The separated, used-to-be Cutie Mark Crusaders. The ponies who are living lost causes. An unsuccessful and exhausted saloon owner, a weapon smuggler (part-time assassin), a gambler who is in dire need of money to keep hide on her bones.

Don't live in Ponyville anymore. Don't even live together or talk to each other.
Their sisters, out of sight and (probably) out of mind. Their friends, they don't care about. Their home, left and abandoned by themselves. Their lives, full of desolation and ruin.