Wild,
I sympathize with you having a "problem" child, I have a couple myself.
INHO, paying for her rent, is enabling.
No one can change her, but her. No matter how maybe times everyone tries to "help" her, it's all up to her. Which you already know from Alanon.
I've tried to help...
paying rent, cleaning their apartment, buying them food, paying their bills...I could go on forever. And all it did was make me poorer and them less responsible.
My heart hurts for you...
"Worry is interest paid on trouble before it is due."
William R. Inge