Thank you for your question.
Massachusetts is, as you may know, an at will
employment state. This means that unless an employee has an employment contract
or union agreement (which may provide them additional on the job protections) an employee may be terminated at any time, for any reason, with or without cause - an employer does not need a reason to terminate an employee. There is no law that says an employer has to be nice, or tell the truth, or that they cannot make statements such as "I will not tolerate you complaining to my boss about me behind my back" because, realistically, if an employer wants to terminate an employee just because - they can.
That said, there are a couple of exceptions. An employer cannot terminate an employee for an unlawful reason - such as their age, sex, disability, religion, race or national origin. You mention your mother is 60, and I don't know if there has been any indication that she is treated differently than younger employees or singled out because of age - but certainly if she can demonstrate that her age is making her a target, that could be grounds for a potential lawsuit.
An employer also cannot terminate an employee due to public policy
reasons. Examples of public policy would be things like an employee terminated because they voted (which is a legal right), or because they refuse to do something illegal (like file false tax returns) and are then terminated.
Outside of these limited exceptions, however, employers do have a lot of power, and the ability to terminate at will employees with or without cause.