Well, I've been further devolping th idea and it looks more like this now -
Blossomforth moves to Ponyville, already knowing about the princesses.
She moves into the house near Lyra and Octavia's studio. She learns that the princesses are expanding their kingdoms into each other's territory and beginning to squabble. After the six ponies (Lyra, Bon Bon, Octavia, Derpy and Blossomforth) confront Twilight, she admits that the subjects are becoming unnaturally greedy and wanting their kingdom to be bigger. Three elements (Rarity, Applejack and Fluttershy staying behind) and three background ponies (excluding Octavia, Bon Bon, and Derpy) go in search of Celestia and Luna, whom Twilight claimed left Equestria after making the Elements princesses, and ask for their help. It is revealed Twilight exiled her because she was possessed by a spirit of greed and jealousy. The greed turns out to be a spell spread by Evil!Celestia out of spite. Celestia claims that the greed will only leave Ponyville if the princesses horns and/or wings are cut off in front of their subjects. When they arrive back in Equestria, Ponyville and the kingdoms have been torn apart by the greedy populace.The six background ponies hunt down the princesses one by one and cut off their horns and wings. The population's sadness and rage burns out the greed spell and they turn on the six background ponies. The BG ponies and princesses then flee. The princesses and BG ponies hide in a reclusive part of a mountain and plan to excorsize the greed spirit. The BG ponies that stayed behind tell about the greed demon, Abraxa. She used to move the various celestial in the sky, but when Celestia came about, she was overcome with greed and jealousy, and possessed her. She has waited a long time to strike. Abraxa ups and leaves when the ponies try to excorsize her, claiming she will return.