Is this mild cognitive impairment (MCI)?

If you weren't there at the appointment, it's entirely possible that Mom is understating what he said. Either way, it's time for a full neuro workup by a neurologist that specializes in Alzheimer's.

Sounds like the Dr has little experience with geriatric care and the aging process..
Medicare patients are a huge burden on Drs because of th elow rate of reimbursement aand some won't even accept them.
This is not meant to fault the Dr but to explain that geriatric medicine has no interest to her. this does not seem to have a great focus on the training of healthcare professions unless they have an interest and seek it out.
try and find a dr in your area who specializes in gerialric care. i certainly would not trust what Mom is telling you unless you heard it yourself. Some people hide a lot from their children because they don't want to worry them others love everyone to know there most intimate details.
Do you know if mom's employer reduced her duties because she was no longer as competent or simply to make life easier for her rather than force retirement.
I worked till I was 68 and no one reduced my responsibilities. Even after i retired i was offered per diem work.

Sounds like the doctor does not want to be bothered with seeing if something is wrong

"Just aging." Did you ask the doctor to explain how the symptoms you describe were compatible with this opinion? In a working woman of under 70?

Were you yourself there at the appointment?

Get a second opinion.

What kind of doctor is your mom seeing? Has your mom been diagnosed with Mild Cognitive Impairment? What does your mom say about it? Has she appointed a Durable POA and HCPOA just in case? Does she want to know if she has AD, if it does turn out that is what she has? If she does, I might consult with a neurologist who focuses on dementia conditions and seek more info. They can order brain scans and neuropsychological exams, that can provide more information. It might give a baseline, so she would know if things later progress. It's a tough situation, but, as long as she's competent, I'd take her lead on how much she wants to learn about it. The things that you have observed sound concerning. They sound familiar to me and not unlike what I have witnessed in some people who start with cognitive impairment. But, there could be other explanations, like vitamin deficiency, medication reaction, UTI, etc. I'd try to rule out other causes.

Just aging? At 69? Is this doctor so incredibly young that s/he thinks it normal for a 69 year old would have any kind of cognitive deficits at all?... lots of people are fully employed up until they are 70 and beyond. Is this doc aware of your family history?
Beyond that, why are you speaking with her doctor at all, I certainly never was privy to my mom's healthcare needs/diagnosis when she was that age, even when she was much older and I drove her to appointments I waited while she went in to her doctor. The doctor certainly can't speak to you at all unless your mom gives him/her permission to do so, so if you are having information relayed by your mom she may not be telling you the whole story.