Maybe see if you can add some extra counseling session in there and discuss with your therapist a plan to put together some healthy boundaries for yourself.
I agree, I would not pay for an apartment for her at this point in time. She’s really not demonstrated responsibility yet. She left long term rehab after only 3 days, not a good sign she will stay on a good recovery path.
I understand how frustrating this must be for you and how difficult it must feel to keep trying to control her and how she should be living her life.
Have you given any thought to support groups like al-anon, nar-anon, celebrate recovery? There may even be a support group in your area for mental health issues with family members.