Your best bet would be to contact an attorney in your area that specializes in legal guardianship of adults specific to your state and case. What I can tell you though is when abuse is supected of an adult who lacks the capacity to take care of herself or to manage financial affairs, often a family member is appointed by the court as guardian or conservator if they do not have a Durable Power of Attorney and/or an Advanced Medical Directive.
You must first institute a court proceeding with attorney assistance. Then a petition is filed for an appointment that includes a narrative presentation of the facts, the relationship to the person, and an explanation as to why you should be appointed. The petition must be accompanied by a certificate of a qualified medical person verifying the incapacity of the individual and why there is a need for guardianship. The court will then hold a hearing on your petition.
Hope this helps.