now that is seriously f*cked up.....I'm hoping that others in your family join in letting the sister know exactly what kind of crap she's pulling, perhaps even telling her "You want it this way, fine, buh-bye".
okay, at least that's how I feel (booting her from the family), but that's just me.
best of luck man, hoping your dad pulls through....or at least the time you have with him is worthwhile for both of you.
as for drinking, bleck. I won't be drinking tonight! join the non-drinkers!