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...
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.
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....