Sam, you're very right to be concerned. As recent as a decade ago, doctors (mostly men) assumed that once a woman was past child-bearing age, the uterus and ovaries were superfluous-- just vestigial, useless organs that cause nothing but trouble. I'd like to see those same men step up to voluntarily have their testicles removed just because they don't plan to breed anymore.
It's now known, of course, that the ovaries and even the uterus continue to produce hormones throughout life, and that this is very important to a woman's health. It could be that your mom's doc is old school and still maintains outdated beliefs. Your mom should run, not walk, to another doctor to get at least a second opinion, and maybe even a third and fourth before amputating an important part of her body.
Well said Lono!!