The most important ingredient is one that no one outside of her can provide: her own genuine desire to change. All of the love, housing, financial help, and family support in the world will not override a lack of internal motivation. People who stay clean after release do so because they want a different life badly enough to work for it every day. People who return to using do so because on some level the pull of the old life is still stronger than the discomfort of building a new one. That calculus is hers alone.
What you can do from the outside is create conditions that make change easier without enabling behavior that works against it. Stable housing matters. Employment or a path toward it matters. Access to continuing treatment, outpatient programming, or support groups like NA gives her structure and community around people who understand what she is going through. Removing the people and environments from her life that were connected to the drug use is one of the hardest but most important factors.
Your role as her parent is to love her without absorbing the consequences of the choices that belong to her. That means being present and supportive without covering for her, rescuing her from outcomes she created, or pretending that the behavior you are witnessing is not what it is. Al-Anon exists specifically for family members navigating exactly this, and it is worth looking into for your own sake as much as for hers.
She has a real chance if she wants it.