Depression and all the stuff tied into it like you mention is one of the most difficult illnesses to treat. I know as a mental health provider I often feel helpless when I work with severely depressed clients. The first thing I can recommend is for you and your family to get support in ways to deal with your sister. Family support groups can work wonders and help you identify resources in your community for your sister. A good place to find info is through the NAMI website. I think it is
www.nami.org. It should list a chapter in your community and also have links for other resources. I can tell your sister is not ready for work at this point in her life. If in the future, she is, there are programs like Supported Employment or VESID (don't know the term in your state) which help people with severe illnesses maintain employment. Basically how it works is she would have the option to disclose to her employer that she is sick and may need to be out of work from time to time and then they can't fire her. Regarding the medication, it doesn't make you feel better overnight. It takes weeks sometimes for a severely depressed person to start to feel better, and because of this, this is usually the reason they take their self off it because they can't see the bigger picture and hope of feeling better. At this point, and from how severe things sound from your post, I can only really recommend an inpatient hospitalization for a long time so she can at least allow the meds to work through her system.