Alzheimers diagnosis.....how important is is it to have that label?

There currently is no cure for dementia, not by medication or anything else. Medications are often given to help with symptoms. And some medications are "thought to help" but unproven, and make of our seniors often enough the cash-cows of the pharmaceutical companies.
I must assume that you have in place DPOA or POA and paperwork, wills and etc are set up so that you will be able to protect your Mom. She will still be capable of taking care of these things, but when diagnosed with dementia and unable to answer questions of any examining Lawyer to prove that she understands the directions she is setting up, it will be too late.
Remember, in early dementia the long term memories are strong, but what you watched on TV together last night are NOT.
Now as to testing, that is going to be hard to force on someone who is currently having memory problems only. What other symptoms are you seeing? Are you Medical POA and can you suggest to her MD that he examine for some of these issues on a regular yearly exam?
What matters now are issues of safety for Mom. You can start a diary on your own of things that worry you that you are seeing. One of the hallmarks of early dementia would be anger and defensiveness when the subject is brought up. For instance if you said to me "Mom, can I talk to you about a few instances I have noted that are of concern to me " I would say "Sure." And if these instances were honestly presented--well, I guess I would say "ONE of us is sure suffering from a mental deficit. I am 78, so I better get tested FIRST" hee hee. If you see what I mean, the kickback is hard when there is fear and often someone who is in the beginning stages is noticing things him or herself that are worrisome.
Wishing you good luck going forward.

There may not be a cure for Alzheimer's but there are treatments, and then there are all the things that may look like Alzheimer's but are not such as vitamin B12 deficiency, UTIs, small strokes and vascular disease, tumours, normal pressure hydrocephalus, polypharmacy and medication side effects.

You are making an assumption of what her cognitive/health issue is. She could have a UTI which in the elderly the only symptoms are often not physical, but cognitive and can mimic dementia (like behavior changes and confusion) but can be treated with antibiotics. At this point is it ok to employ a "therapeutic fib" to take her to the doctor, like: Medicare now requires an annual physical. Once there hand someone a pre-written note outlining your concerns, request a test for UTI and also a cognitive exam.

There is no medicine that "helps" Alzheimer's like I think you are implying. But ALZ can have a different prognosis than dementia. Does anyone have durable PoA for her? Someone other than her now needs to be closely involved in her medical care. If she has something other than a UTI, she will need an advocate with her at ALL appointments and even if she needs to take meds.

Your jumping the gun in assuming she has AD. AD is a disease that manifests itself by the presence of certain symptoms. These symptoms are called dementia. Dementia is a lack of brain function along with having difficulty in performing certain activities of daily living. There are over 70 different reasons that cause dementia symptoms, some are treatable and even reversible, some are not, AD being one. Your mom's PCP can administer some very basic cognitive tests, along with getting family history. If dementia is suspected, the PCP can refer her to a neurologist. I like the idea of telling her it's time for her annual checkup. Medicare pays for an annual physical. So you're way ahead of the game by assuming she may have AD. You can't determine that and neither can her PCP, it takes a specialist. But the PCP can evaluate her for dementia. Once you get a drs evaluation, you'll know what you're dealing with. Without a diagnosis you won't know what to expect, how to prepare for it or how to care for her.

It is important to initially find out what type of Dementia she has since certain medications can't be used with certain Dementias. ALZ effects the brain differently than other Dementia's. As suggested start with a good physical with labs. If Mom is on a water pill then her pottasium can be effected causing depression and other things. B12 maybe needed. UTI. Thyroid. Its been found Statins cause cognitive problems. If nothing is found, then a neurological work up can be done. Mom could behaving little strokes.