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.
If there are no medical issues found, how to proceed is dependent on how she is doing. If it is dementia and she only has short term memory issues, she is only in the early stages. Progression is unique for each person. While she is in this early stage, if dementia is indicated, I would read everything you can about dementia, symptoms, stages, how to deal with various symptoms, behaviors, etc. Being armed with information will help you during the progression. It was how I learned about it and it enabled me to recognize what was going on and how to deal with it - diversions, redirecting focus, not arguing, explaining or correcting, just learn to go with the flow!
The reason why someone has developed dementia-like symptoms would only apply if testing proved the symptoms to be caused by something else, not dementia. They don't fully understand at this point WHY someone gets dementia (exceptions may be repeated concussions or vascular, which can limit blood supply in the brain and can cause atrophy.)
There is no real treatment for dementia, only to counteract symptoms. IF your mom starts to have some serious issues, then consider more testing and/or neurologist. Given her great health and some memory issues, I wouldn't subject her to any extensive tests.
The only reason to determine the type of dementia is for LBD, which has a different progression and can be made worse with some medications. Generally, based on symptoms and behaviors, it is possible to differentiate in the earlier stages without invasive testing. Otherwise, testing isn't going to help much.
Keep mom as active as possible. Include socialization if possible (some become reclusive.) Exercise, even just a good walk every day or so, is beneficial. Have her participate in any/all home activities that she can physically manage - this keeps her active, stimulates her, makes her feel productive (even if you have to redo whatever later, when she isn't watching, just like with kids!)
https://www.medicalnewstoday.com/articles/324877.php#1
There are many dementias. What if mom has B12 deficiency? thyroid out of kilter?]
Start with a good work up from her MD....or from a gerontologist or neurologist. Keep records. Weigh every visit; try to keep the annual physical going to monitor trends. As communication becomes less...finding problems can be simplified some by knowing her 'norms' Doing annual lab work may find that something else is going on too. If the time comes to use hospice, for instance, you will find qualifying much easier if you can show downward trends in the albumin levels..
If the physician assessing your mom - does say Alzheimer's...and you have done your research and feel that something isn't adding up - say so. Help them dig. Folks can have a mixed dementia - Alzheimer's + vascular, for instance. Be reasonable...by asking yourself what you would want your son/daughter to do for you in this situation.
Don't throw in the towel yet.
Carry on, as is. I think you already know the answer to your question.