My mom did the same thing......she has a tendency to live in her own la-la land where all her children are wealthy, perfect, and important.

Eventually, she has started to come around. Don't forget, many people of her generation (she's 73) disregarded weakness, mental illness, and looked at the world from a completely different perspective when they were growing up. People with MI were put into sanatoriums or lobotomized, treated as defective human beings. Medical treatment back then was bordering on inhumane but the stigma was real. So many people of my mom's generation cringe when discussing mental illness.

I took it upon myself to become educated about BP......I had no idea what it was when the doctor said "you're probably bipolar". My reply was "wtf is that"? I then passed that knowledge along to my mom who is good enough to listen and tries to understand. I don't necessarily think she has bought it 100%. Like your mom, she also thinks the diagnosis could be a "mistake" but I know better. I took it, ran with it, and got better so she's seeing the proof.

In short, sometimes "old people" go into complete denial when it comes to modern society.