Can a Parkinson’s Dementia patient go from no symptoms to being completely dependent within 6 months?

My 86 yr old Mother had minor outpatient surgery on her hand 6 months ago. General anesthesia was used. She has had VERY SLIGHT, MINOR tremors for many, many years. Never diagnosed with Parkinsons.
Minor surgery, shouldn't be a problem. She is a very active, in good shape, runs rings around her 4 children, just never stops. Great seamstress, great cook. People mistook her for a 70 yr old all the time. What the heck did we know?? Apparently NOTHING! When she came home from the surgery she was different person. Nothing drastic, but just slightly different. We thought it was the anestesia not completely out of her system. We (I am 1 of 4 children, 3 girls live fairly close to my parents, my brother lives 1200 miles away) would call her on the phone to check on her and my Dad (he was diagnosed with Dementia 4 years ago) and to see how things were. All sounded pretty normal. Us 3 kids would stop in periodically for short viisits at various times checking up on them but we didn't stay for too long. An hour or two at a time. Things just didn't seem "normal" but I couldn't put my finger on it.
I decided to come for an entire day and spend the night to see what was going on. Within that month, she had gone from doing everything herself to not being able to do much of anything at all. She was overdosing my Dad on his meds, forgetting some of them completely. Just was so out of character for her, she was unable to care for him let alone herself. I then moved in with them for 5 - 6 days a week. My other 2 sisters take the other 2 days and come in for them. As stated, my Father was diagnosed with Dementia about 4 years ago, is on meds and he is doing fantasic. He does have problems, but for his age (86) and diagnosis, he is actually doing better than she is. My Mother is now at the point that she is forgetting just about everything. She is getting things mixed up, she is totally confused most of the time. She has caught a couple things on fire on the stove. Set off the fire alarm and didn't know what it was, and didn't smell the smoke from the fire! I am now doing most of the cooking, My sister has had to take over the bills. And the clencher tonight..... my brother had surgery today and she didn't even remember. She just looked at me when I told her that he was in recovery and all was good. She had nothing to say, like she didn't know what, or who, I was talking about. Just the blank stare. This is the lady that was fighting with me 2 weeks ago that "no matter what the doctor says, I am a good driver and I will drive if I want to!" Then she took the Drivers Evaluation AND PASSED IT!! And tonight she can't remember that her son had surgery today after I told her 6 hours earlier that he had just gone into surgery. One minute we are together in one room, then she goes into another and forgets that we were just together in another one. Not just talking and not remembering, but now we are in physical contact with each other and she turns around and doesn't remember it. She tells me we are having for dinner and goes to the refrigerator and either forgets what she went for or pulls out something totally different. It's just like that all day. Between her and my Dad I do nothing but follow them around all day.
What I am wondering,.... Since my mother's story of what may have happened to her, Parkinsons Dementia onset from surgery, has anyone ever heard of such a QUICK decline in mental functions and capabiities? "Normal" to 24/7 care in 6 months???