Zeraph, I understand your situation, and how you are trying to make it better. However, by continuing on this path of rescuing your mom, and not insisting on certain standards of behavior from your sister, you are enabling the situation.
I used to be the queen of enabling. I know whereof I speak.
You have to set your boundries (raeanna74 has *superb* input there), and *you* have to enforce them. You are not responsible for anyone but yourself in this situation, and you cannot control anyone but yourself.
If you don't make a stand, you will be stuck in this cycle for the rest of your life.
Personally, I'd fix the fan while your sister helps, and charge your mom $75. Cash. In advance. It's a win-win-win situation.
