Hereiam,
First of all, .....sad isn't it??? They have 'all the power'.....and the wield it.
I'm a former elder....recently fading. I have a great deal of experience on JC's (unfortunately).....Here is my advice:
Tell her to cease ALL contact. Do not answer letters. Do NOT answer phone calls. If necessary, tell her to make a new rule for herself: if the number comes up on caller I.D. as one she doesn't know....do NOT ANSWER IT. If any JW outside of the immediate family she wants to keep make an attempt to contact her, do NOT answer them in any way! Especially not your mother!
What state do you live in? Check to see if their are harrassment or stalker laws. If, for some reason, she comes into contact with them.....(she should avoid them at all cost)...... she can say "I don't know what you're talking about......do you have 2 witnesses to this?" If they say yes, she can say "according to Matt. 18 they can approach me.....".......but she should otherwise DENY anything.
If they press her on "do you want to be a JW?"......tell her to respond with "I'll answer that if you can answer this: According to Gal. 6:1, if you felt I was making a false step, you were supposed to shepherd me YEARS ago........ why didn't you do that? I have nothing further to say to you..... My attorney has kept track of every phone call and letter..... the next effort to contact me will trigger him into action. I am going to let him know you attempted to communicate with me today. Have a nice day."
Avoid them at all cost. But the hint of a legal complication will send the vast majority of inexperienced 'elders' running......