I would stay out of it and let her feel the full weight of the consequences of her actions. If she gets out of jail early it should be because she demonstrated she is a changed person, not because you came in and saved the day by giving testimony.
I also wouldn't do anything to speed up the process of her getting out into the real world. In jail she is safe, has a better chance of staying sober, and has a routine she has to stick to. If she gets out, well all hell can go loose. I wouldn't put any weight on any of her promises until you saw some action from her.
I would allow her life to fall into place based on her actions not yours (helping her get out by giving testimony). We are all responsible for our own lives and right now, it is more important that you take care of yourself and get to a good emotional point. If she got out early there is also a big chance that she will bring you down with her emotionally and physically if she goes back to using or ends up sucking you dry financially.
Do what is best for you. Don't make any decisions based on making her life easier because in the end the easier her consequences go away, the higher the chance she does the same thing again.