My mother's situation is complicated by being a dual citizen – she'd have to update all her paperwork with the governments of two separate countries.
I am also a dual citizen, so would have the same issue – except unlike my mother, I can't think of any plausible reason why I might want to change my legal name.
It's totally understandable why your mother would come to her decision, even without that aspect but especially with.
I just found it interesting that someone else chose otherwise, at an even older age than your mother.
According to Wikipedia, he changed is name in 1988, at age 58. So I guess he changed his name in the 80s, not his 80s. Still fairly late in life to change your name, though!
(And "Buzz" came from one of his sisters misprounouncing "brother" as "buzzer". What a cute origin!)
Unrelated fact about Aldrin: his mother's maiden name was Moon. Bit of nominative determinism by proxy there.