Greetings, rather be in hades.
I would first ask her that if the "brothers" do not claim to be inspired and never have.. and have admitted that they make mistakes in doctrine, then why should anyone view what is published in the WTS' literature to be the teachings of God and not men? Then have her look up the following article on her CD. It's only from 2010, so it's pretty recent.
*** w10 9/15 p. 13 par. 8 Unity Identifies True Worship ***
The Governing Body publishes spiritually encouraging literature in many languages. This spiritual food is based on God’s Word. Thus, what is taught is not from men but from Jehovah.
Ask her what she thinks about imperfect unispired men publishing such a thing about thier very own literature. Because if they can make such a statement, then anyone who publishes literature that it's based on the Bible can make the same statement and your Mom whould have to believe them if she is going to believe the men who make up the gb residing at WTS headquarters. If men claim that they are unispired, then they are OUTRIGHT LYING in claiming that what they teach in thier literature is not from men, but from God.
I don't have too much time at the moment so I'll just say that I think you've been given some great advice here from posters and that I'm sorry you have to go through this. My thoughts are with you and your mom. Cults REALLY DO SUCK!
peace to you,
somebody/gwen