My sister went through this with her daughter a few years ago. Sister took everything out of daughter's room except for mattress and a few clothes. She even took the bedroom door off the hinges. She would take the phone to work with her and had the tv unhooked and the comp. locked down. She locked up all the food and would leave cans of soup or beans for daughter. It got old pretty fast.
Daughter got a job and went back to school and got a teaching degree. Daughter says she owes everything to her mother for loving her enough to lay down the law and mean it.