Hello, I can understand your distress.
Such a behaviour in her age group could indicate possible brain condition. If the behavioral change has been abrupt and sudden, there is a strong possiblity of dementia problem. Depression, psychosis , personality changes are common problems at this age.
There is a need to investigate further.
A brain MRI scan can yield valuable information.
A detailed psychiatric workup is needed.
Next Steps
My strong suggestion to you is to show her to nearby psychiatrist. With suitable medications her behavioral problems can be controlled. There may not be much a role of counseling at this age.