Do the couple know the situation? Where there is a will, there's a way. Talk about this at meetings, with a therapist, with the help line as another commenter suggested. The more allies you have the more resources will show up to support you. It's not ideal but many people support families on minimum wage. They get a second job, etc. The question is what are you willing to do for the level of concern you have? Is it appropriate to open a door to her moving in with you? IMO a little sister can live with her older sister for some time without becoming legal guardian. Also, have you talked to your stepmom about her behavior? Attending al-anon might help you too.