No endorsements here, but Women for Sobriety may be a worthwhile female-only environment to avoid the many challenges New Chapter mentions for women in AA. Instead of 12 steps, they have 13 affirmations which appear helpful for recovering JWs, too.
Many links for "Non-cult Pro-Recovery" at http://www.orange-papers.org/. Again, cannot offer any endorsements but there's lots of non-AA resources to wade through there.
Addicts typically eat poorly. Most suffer from nutritional deficiencies. Since your niece qualifies for government assistance, is it possible for her to access a nutritionist who can help her heal and rebuild her whole body? Rehab therapy and/or meds can only go so far if she is physically run down from the inside out. Fresh fruits and veggies, low carbs to avoid blood sugar swings, and plenty of water daily to stay hydrated are so key even for non-addicts. Maybe a vitamin/mineral or protein supplement? Women in particular need extra iron… and B-complex can do wonders for people under stress, yet alone recovering from addiction.
WhereWasI, best wishes for strength and peace for your family as you advocate for your niece, and especially for her healthy outcome.
~Sue