姐妹一旦变脸就变后宫甄嬛
[jiĕ mèi yī dàn biàn liăn jiù biàn hòu gōng zhēn huán]
A reference to 'Empresses in the Palace,' where the character Zhen Huan faces court politics and rivalries. It reflects a shift from sisterly affection to rivalry within a group dynamic.