I'm so sorry for you and your family.
I don't mean to state the obvious here but something has to give. And unfortunately you are the only ones that can force the issue because you support her. Are there people in her life who would make her rethink things who might help with an intervention?
Not everyone believes in the rock bottom theory of change, but she certainly won't make any effort if she has no incentive. There are alternatives to cold turkey 12-step program, like CRAFT or SMART recovery (also called harm reduction). There are medications to help her handle alcohol cravings.
And perhaps you can pull some supports initially to leverage some movement. Off the top of my head, she shouldn't have a lock in YOUR house. You would also be well within your rights to press charges for theft and perhaps she would get court ordered treatment. At the end of the day, though, you have to be prepared to stop being party to her self destruction and that may mean you put her out unless she is in treatment.
