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.