God love you. Like you said, you have no authority. Now she has Dementia/ALZ she is not legally able to assign a POA. A guardianship is next and believe me you don't want that responsibility. You report to the state. Medicaid could come in an evaluate her for homecare. Office of Aging may have some aides or programs. Her Dementia will only get worse. It could be slow progressing or change overnight. You may want to try APS. If no one to care for her, she may need to be placed in a NH. So sad.
A call to APS, your local senior center might also help. Not their job but often the Police Department might be able to help. If you feel up to it you could become her guardian. It is not an easy job but it is not unheard of that a friend or neighbor becomes a guardian. (as part of the process the court would have to contact family) If you can find out where her relatives are you could get in touch with them They may be aware of what is going on and keeping out of the picture for a reason or they may be unaware of her condition and would be willing to step in to help out. But again at least you have done what you can given the circumstances.
If you feel up to it you could become her guardian. It is not an easy job but it is not unheard of that a friend or neighbor becomes a guardian. (as part of the process the court would have to contact family)
If you can find out where her relatives are you could get in touch with them They may be aware of what is going on and keeping out of the picture for a reason or they may be unaware of her condition and would be willing to step in to help out. But again at least you have done what you can given the circumstances.