It's great that your mother felt confident standing up to abuse. Not everyone does — and someone early in their career, knowing that their entire life trajectory can be affected by their boss's reviews and networking, is going to feel different than, say, an established figure in the field or a worker at a union shop who can expect their support. The author of this article appears to have gone to Google directly from college and it's only reasonable to worry about jeopardizing your first big job by leaving quickly.
The other thing to pay attention to is the nature of the abuse. It's easy to reject some guy who makes a crude leer in front of witnesses. Her former boss was apparently more subtle than that since he managed to get at least one female coworker to take his side excusing his behavior.
That's not an accident - the men who do this kind of thing usually aren't the crude street-harassers of stereotype and are smart enough to pick women who are more likely to be vulnerable while leaving as little clear evidence as possible.