Suspicious

My mom is 81.  She has always been very active and physically healthy, although she did have a stroke 6 years ago which she seems to have recovered from fully - physically any way.  Over the last few years, she has become progressively more "suspicious" -  adding screening, glass blocks, etc around her balcony.  Over the last 12 - 18 months, she has changed her locks 3 or 4 times.  Then she started to say things were being stolen from her - small things, utensils out of the kitchen, table top pictures frames, and she says people are changing things - changed her towel rack in her bathroom, her bath mats, changed her shortening from "tenderflake" to "that no name brand".  She has changed her mind numerous times as to who she thinks it is.  She recently went to the police with these accusations and they ultimately called me (I am the only remaining family member) to see what I thought of their validity.  My mom lives about 5 hours drive away.  If I question or doubt her accusations, she becomes very angry and says "you think I don't know my own bath mats?!"  It is becoming very difficult to deal with.  She has also accused my husband of having an affair which has caused extreme hard feelings.  I have contacted her doctor and he is conducting some tests.  Don't know what to expect from here - even if she is diagnosed with dementia/alzheimers - and is put on some medication, is there ever a point where she will become logical again or is this forever now??