Hi VirgoChk... are you your Mom's Power of Attorney? If this has not been setup yet, I suggest you get it done.
You and I are close in age. I used to tell my folks things like "You don't have to worry. Jehovah knows what's on my heart" or "Jehovah reads my heart so not to worry." I am lucky as I never got baptized so my parents had the technicality that I wasn't really a JW. They could still associate with me. If you were baptized you definitely have to tread lightly. Does your Mom believe that all non-JWs are going to be destroyed at Armageddon? I found my folks used to waffle on this. They knew that there were good non-JWs in the world, especially those who put their lives on the line protecting, healing, educating, and feeding others.
I like Daniel's suggestion as well. It was very difficult at times but I had to ensure that I showed my parents unconditional love. I also tried to live my life as a good person; to be an example of a non-JW who wasn't evil. I find JW's are actually very afraid especially for their loved ones not in the religion. I think it's our job to reassure them that all is well and not to worry. I would also ask questions that weren't directly pointed at the religion. Since you are close to my age, sounds like you, too, have experienced the failure of Armageddon to arrive 'soon' for your entire life. If my folks pushed their agenda I would ask what their definition of the word 'soon' is. I would say "If I told you I was coming to your house 'soon', and 50 years passed and I never showed up, would you still think I was coming 'soon'? I liked to ask them questions that would get them thinking logically.
So any discussions I would have with my parents I tried not to badmouth the religion, but rather point to specific issues I saw especially Biblical ones. For example, I had a discussion with my Dad about Abraham Sarah and Hagar and how wrong it was for God to sanction this. He and I were on the same page about that story. Try to find some common ground that affirms both of your beliefs (like helping the less fortunate for example) and then ask how she has done that lately? Perhaps give her examples of what you are doing.
Again, my goal was always to:
a) Show unconditional love. Treat your Mom with respect. Make her feel good. Compliment her on things. Keep the mood positive.
b) Remain Calm. Do not react negatively or get angry when they got emotionally abusive (this is very difficult to do at first but it can be done. You need to practice. Maybe get your husband to help you with actual scenarios).
c) Listen to what they are saying and point out, nicely, any logical fallacy. Never directly badmouth the religion.