If your social security benefits are being stolen or misused, the SSA would be interested in knowing about that. You could call your local Social Security office to report it and, if you need assistance managing your benefits, they can assist you in getting a Rep Payee set up. If you don't have an individual in your life you think you could trust for that purpose, a professional from an organization that offers Rep Payee services can be appointed.
Are you dependent upon your sister for housing or other key needs? If so, I might be concerned about the ripple effect that reporting her for Social Security fraud might have for you, though, and if it will cause the relationship to deteriorate further.
If you are considered care dependent due to your disability, some states have protective services programs that will be able to help you, even if you are not yet elderly. If your state has that available, you can self-report abuse or fraud and someone will investigate and help you with finding alternate living arrangements, if needed. But, they will only help remove you from the situation if they determine it's warranted and that the circumstances meet their definition of abuse, fraud, etc.