Miss diagnosing early dementia as depression is actually not uncommon. The early symptoms of dementia are almost identical to those of depressions. My Mom was misdiagnosed for almost 2 years with depression when in fact it was Alzheimer's. That is why more extensive testing is needed. Your Mom probably scored in the upper 20's on the MMSE which is not a horrible score but it is indicative of early problem. They see the depression symptoms and go no further. If there is a score on the MMSE below 29... there is a problem. We all wish that the problem is depression. That way we give them a pill land it goes away. The problem is that if it does not go away you are another six months to a year into the dementia without knowing.
There is evidence that surgery/medical trauma can accelerate cognitive decline. It has only recently been studied and a connection was found but more extensive research needs to be done into why. Even during all the years that the medical profession was denying the problem, those of us with loved ones who have dementia knew of it's connection. Yet sometimes the surgery is necessary and there is nothing you can do to change the outcome.
I would not take her off her blood pressure medication or blood thinners but there is no reason to leave her on Statin. The first two medications will thin her blood and control her blood pressure. They have an immediate effect and when you stop taking the pills the effect goes away causing a critical situation almost immediately. With the Statin, it lowers the cholesterol level in the blood over time. Cholesterol, unlike the other two situations, is not something that will cause an immediate problem. Cholesterol build up takes years. Taking it or not taking it has no immediate effect. It is more of a preventative for some time in the future. I took both of my parents off Statins in 2007. Dad, even with his heart condition, live for another three years. Mom is still alive with not adverse effects. On the other side of the coin I took statins for almost a year with major side effects. Cholesterol is actually brain food. With the lowered Cholesterol levels I went into a mimic state of cognitive decline. I also suffered from depression like symptoms. I forgot my medication and did not take it for two weeks, only to return to normal, and realized my symptoms were all a result of the Statin. That is a rare side effect but one that is now recognized. After that experience, knowing what I know about Statin, I DCed the medication for both my parents... with no effects at all.
On the first consultation your Mum should get a complete physical with blood work to make sure there are no health problems that could cause her cognitive decline. There should be a complete review of all her medication as well. She should be given the MMSE and any score below a 29 should be followed up with further cognitive testing. She may also receive a CT scan or MRI to rule out any condition of the brain that could cause the problem. If there is shrinkage of the brain that is an indication that dementia may be present. If she has been treated unsuccessfully with antidepressants, that rules out depression as the cause. Since there is no one stop test that diagnoses cognitive decline, diagnosis is a process of eliminating all the other possibilities and looking at the symptoms. That is why it is imperative that you give them all the information possible on her behavior and cognitive function.
Try to keep a journal between now of anything that you think might be important. This will give you a better feel for what is going on and what you need to talk to the doctor about. It will give you patterns and a time line. When you are in the midst of the chaos it's difficult to remember all the details unless they are written
Hang in there!! You are doing the right things. Learning all you can about the disease is important so you will know what to push for and how to help your Mum. The diagnostic process takes patience and persistence and I see you have both. And know we are here if you need to vent .....