I have gone to caregiver support groups where both caregivers and social workers have told me not to bother. The reason for her dementia is not important since there is nothing that can be done. Other than her forgetfulness, she is in good health. She only takes vitamins. No other medication.
HOWEVER, you may want to get her to agree now to make you her PoA for financial and medical matters. Without that power, you will not be able to make decisions for her if she is incapacitated.
I suggest learning the reason for dementia IS just as important, equally so if there is, or is not, any family history. It allows other family members to come to terms with the possibility/likelihood of them contracting the disease, not to mention planning their own futures, and taking advantage of every research development as it comes along.
If it were not for the guardianship we wouldn't have done this. There is no cure, nothing to help her.
If anything is tested, it should be non-dementia tests to rule out other medical issues, such as UTIs, which can cause dementia-like symptoms and are most often treatable!
I wouldn't go to a neurologist just to determine the type, unless regular testing can't determine if it is something like Frontal Temporal, Lewy Body OR as in your case you need it for guardianship or perhaps some medication is needed to help calm a person who has hallucinations, sun-downing, etc and it is bad enough that it needs some control. Otherwise, it is what it is, testing won't change anything, but getting informed about dementia, the various types, what you might expect and a sample progression WILL help those caring for or advocating for a LO will be better prepared to do what needs to be done! Keep in mind that each person's journey is unique - they have similar symptoms and progressions, but progress at their own rate and experience things differently.
My mom's mental and physical health changed very abruptly in her early 90's and I was left trying to make sense of it all on my own, that's how I found AgingCare. I never did get any help from any of mom's doctors; her GP had previously sent us to a neurologist who was only focused on stroke prevention, despite brain scans neither of them ever discussed any potential for dementia. The ER docs couldn't see beyond her age and more or less told me she was end of life and the nurse who was in charge of her home care told me the same, nevertheless she lived years beyond that point. I'm pretty sure a diagnosis wouldn't have changed anything but it certainly would have helped ME to understand and make plans.
"Dementia mostly affects older people, and the risk of dementia increases with increasing age. ... Nearly 1 in 4 people aged 85-89 have dementia. It is rare for someone under 65 to have dementia, but it does occur at younger ages and we call this 'younger onset dementia'."
With dementia effecting the elderly at almost 25% of the population, doesn't it seem that it IS an inevitable part of aging?