You are doing great, lil.lady! Please know that you are not alone in this!
One of the best things to do with Witnesses (and I'm finally learning this myself) is to ask questions instead of give answers. Asking questions to your mom will be far greater than trying to tell her what is wrong with the organization. For example, start listening to the daily text that she reads to you. If they talk about the "Faithful Slave" you can ask, "Why are we to go to the organization for salvation, when Jesus tells us to come to Him?" If it is speaking about the annointed, you could ask, "If becoming "born of God" is open to "everyone that believes (as spoken of in 1John 5:1) and if the requirement for entering heaven is being "born of God" or "born again" (John 3:5), then isn't the kingdom open to "everyone who believes" and not just 144,000 people?
Or you could ask an even simpler question. "Where in the Bible does it say that the great crowd is exempt from heaven?" Or "Where does it say that the great crowd is relegated to live on earth?"
Questions are more powerful than answers.
Jehovah's Witnesses are told to ONLY ask questions that appear on the bottom of the Watchtower magazine, and that the answers are to be found in the paragraph. So skillfull use of questions can be a good way to possibly get through to your mom.