So my youngest older sister thinks my oldest older sister is bipolar

At this point I agree. Her personality is changing constantly. She threatened to send her teenage daughter she adopted to boot camp. Apparently she wants me and my two other sister to pay 50 dollars for cooking at my mother's birthday. And she owns a restaurant and constantly short comes my other sister who works there for 12 years and does everything. And I agree she's been acting different, weird. Idk worry's me.