Saving Water Despite My Listens-to-Nobody Sister

[mel_pa]

My state is in a severe drought and our household's water bill is still high and we have been trying to save water, I'm working on reusing water and using a cup to scrub myself before rinsing off in the shower. One of our problems is my mentally ill sister's not listening to us when we tell her to save water. Like she stubbornly washes dishes by refusing to do it in the dish water in the sink and runs the water. She resists everything we do to save water and even sabotages our efforts. She re-washes clean dishes stacked to dry and doesn't listen when I tell her those dishes are clean. My step-dad says it's like "talking to a wall!"

I heard there will be stricter restrictions by the state with fines and I'm terrified my sister's behavior will make it impossible to comply. What can I do?