How do I get my mom help when she is in denial?

Knowing is not good enough, without an actual diagnosis of dementia or paranoia from a licensed physician or a review from at least a specialist that's area of expertise is clinical psychologist with a Ph. D., for example. Health records are protected for a reason. If a new doctor, family medicine, primary care doctor is used, you will need to have a release form also from previous doctors signed by a person that is authorized to do that.

If that person is the person that is having a medical issue, it takes the luck of the draw to get any primary doctor to make the referral if that doctor does not see these problems as legitimate concern other than old age or side effects from current medications. This has to be seen by the doctor during the visit to make an assessment, otherwise it's follow-up 3 months, 6 months again to see the trend.

If she knows who she is, is not a fall risk, can still drive or enjoy current lifestyle choices based on age, based on medical conditions, then it is the surroundings or the family dynamic that is pressing the confusion as well. If father or caregiver disagree or refuse requests for improvement, they have the leg up, a bit, because they are their 24x7 more than anyone else.

Often, it is the one that is not living with the issues that sees the problems at face value, and if that person does not have POA or legal rights to improve the situation, very hard to improve without others help. A primary can still diagnose mild cognitive issues, but it will take a specialist to confirm change is needed, i.e. neuro, psychologist, attorney, judge, etc... it's just the way this goes sometimes.

Part of the denial is no one is willing to step up and accept there are better ways to live. They are okay with the ups and downs of normal living, especially if they are okay with the current arrangement. Still have both parents. Could be worse.

Is the caregiver for dad or her?

My mom refused even to have caregivers in the house

Perhaps someone will give you some ideas to get her to the doctor - geriatric or neurological- and perhaps get her on meds

Her behavior is quite common and can last a long while - my mom accused my sister of stealing a chair from her bedroom for years and she constantly hid her checkbook and keys and so on - it was exhausting

unfortunately many of us wait until there is a crisis- a fall or hospitalization before we can get them treatment

Perhaps you can tell her dad has an appointment and you'd like her to go along letting the doctor know ahead of time

When I finally did get mom to the neuro I had to lie and say it was because she hit her head when she fell - at her age I wasn't overly interested in slowing the memory loss but needed to help calm her - the first med did not work for her and so after several months we made a switch to one that makes her easier to handle at least part of the time

She lives w my dad and a care giver - the problem is getting her to go see ANY doctor regarding it - she doesn't think anything is wrong with herself and if I mention it then I'm out to get her

Mary,
Is mom living alone? Perhaps it's time to find a new doctor - 10-15 years sure sounds like a long time