Either you're exaggerating or she's not being completely honest with you. No human is capable of generating unique 20+ char passwords for every service and remembering it. I suppose it's possible you're married to the rain man...

She only really has 5 or so things she has logins for. She also commits her credit card, bank account number and pretty much everything she can to memory.

I think it's a side effect of schooling in South East Asia where she spent most of her childhood wrote memorising.

I don't think she would be able to keep up with the rain man but I don't think I'm exaggerating.

Memorizing 100 random symbols for the most important logins is reasonable, but the average person probably has in the order of 50 logins or so. I just counted and was surprised that my password manager contains over 200 passwords. There is no way that I could memorize that many secure passwords or even passphrases.

FWIW, and I'm not suggesting you actually do this, but you probably could learn to remember that many symbols. People can memorize thousands of digits of pi. People can solve ~60 rubik's cubes in an hour blindfolded (where they must first memorize them). I think, surprisingly, it's actually within the realm of human ability to memorize 200 20 character passwords.

She is clearly the exception and must have an amazing memory!

My dad has 'different secure passwords' for all the different sites he goes on, but curiously whenever he shares logon details if I am helping him it's always the same password! Hmm....