Hi pumpkin, it's sounds like you've gone through some really difficult times with both your mother and your sister, I'm sorry
But with your sister.........people have really got to want to change things, which it's not sounding like your sister is wanting right now?? and even then it can be so much easier said than done to change things.
With the rehabs..........sometimes people have to go through rehab quite a few times for it to start to make a difference and then it can totally depend on the actual rehabs they're going to, some have a much better success rate than others.
And groups like AlAnon...........Narconon can be really helpful, but if your sister isn't interested...........???
Maybe your sister's behaviors/views are a result of MI, people around her, experiences, the way she feels abut herself/her life............maybe a combination of a lot of things??? But ultimately if nothing's getting through to her right now, then you are kind of limited in what you can do for her.
I don't know if your country is one of those where you could write a letter to the court (for before her court date) explaining that you're worried about her and you feel that as part of the processes she should be referred/sent for some help??? She might not thank you for it if she finds out but.............
And perhaps carry on with the "tough love" approach, doesn't mean you can't empathize with her, doesn't mean you can't let her know you'll be there for her when she's committed to getting help.
And you (!!!)..........I know it's got to be hard on you dealing with this, but perhaps limit communication (where you can) to a less stressful level, try to see some of the possible reasons for her behavior, and that some of them she probably isn't going to be able to help right now. Doesn't make them OK, but it might make it easier on you to deal with.
And when you're struggling maybe you could try sharing some of the problems as a family??? Support each other??? Or in the very least make sure that you have some support for yourself.
You could always get some extra support from somewhere like AlAnon too, who also help families.

Alison