Ask a Dog Vet and Get Answers to Your Dog Veterinary Questions
The decision to euthanize a pet is never an easy one and I think your vet's input may be valuable as he or she can provide an unbiased view as well as answer your medical questions. And I think it is absolutely appropriate for a veterinarian to recommend euthanasia as some people will resist making the choice and continue treating a pet that is suffering because it never occurred them to stop. I have even had people tell me that they wanted me to make the decision so they didn't have to.
However, the decision to euthanize your dog or not is ultimately your decision and no one can make it for you. It sounds like she is experiencing signs of dementia or "sundowner's syndrome" as it is called in people. The veterinary term is called canine cognitive dysfunction. There is a medication and supplements that my help halt the progression of the disease but ultimately, this is progressive and is similar to alzheimer's in people. We do not know if this causes her to suffer because we do not know how she perceives it or whether she is aware of the changes occurring. There is little evidence that dogs are aware of their condition just as people with dementia are less aware of their condition as it progresses but it certainly provides us with a concrete reason to elect euthanasia as it is a progressive disorder and one that can also affect your quality of life and your relationship with her, especially if you are becoming frustrated in not being able to soothe her or having to clean up accidents in the house frequently.
When I discuss euthanasia with my own clients, I have them list 3-5 things that defined their pet and his or her quality of life and when he or she is no longer able to do those things or no longer has interest in them, then perhaps it is time as he or she is not the same pet that they know and love and most people elect to euthanize. You shouldn't have to do lots of tests, all you need to do is schedule an appointment and discuss her situation with your vet and it shouldn't be more than a regular office call plus the cost of whatever you decide to do in the end.