Legal Question in Elder Law in Arizona

What you should do is petition the court for appointment as her guardian (and conservator if financial matters are needed)(same cost), however, you will need a doctor's report that she is unable to manage her own affairs. The circumstances that you describe are very common and should be addressed as soon as possible, to maximize her safety and wellbeing, as well as that of your father. You should also consider whether it is in your father's best interests that he live alone. It is my experience that a 90 year old senior should not be living isolated, that he needs social contact and his quality of life would be far better, if he joined his wife and had their assistance with meal preparation, cleaning, laundry, transportation, etc., and that is usually much less expensive than the cost of maintaining a separate residence (and your step mother would probably drop her ideas about coming home).

You can consult with me for a small fee and discuss the options available to you, and then decide how to proceed.