What should be the next step for 98 yr old that lives by herself in her own home and has recently started show signs of mental instability?

Appointment of POA if the elder is still able mentally to do this.
Assessment and diagnosis in order to stage capabilities to act for self. Appointment of guardian or conservator is the elder is diagnosed unable to act in own best interest due to mental incapacity. Placement in safe environment with assets protected against fraud and/or theft.