@vickers6504,
And that proves that the odor is created by bacteria. Possibly you use more water than Mom, or you have more regenerations due to a larger family size, which means more bacteria running through your softener than hers and you have the problem, she doesn't.
So sanitize your softener when you start smelling the odor, or figure out something else or... live with it; what other choice do you have, I don't know of any?