I'd tell such an irresponsible person that, since she is abandoning me and everybody else with her irresponsible behavior over the house, etc., that it's all over - starting right now! I sure wouldn't let some abstract cliche like: "It's my obligation to support an irresponsible family member." to govern my COMMON SENSE! I'd tell her "Sorry sis, but my family needs my share of the money just as much as you and they COME FIRST!" I'd let such a loser sink or swim and stick by my own kids and spouse!
jim