I think you need to respect the beliefs of your mother. Remember that this religion is all she has to hang onto and that it brings her happiness. To wrench it from her in the sunset of her life without having a replacement would destroy that happiness. If she finds it fulfilling, why would you want to take it away from her and leave her with nothing?
If the WBTS is wrong (and I agree that it is), its doctrines are wrong and must be rethought. All that stuff about Christmas, Easter and uniforms, not to mention blood, is back at square one. The doctrine of life after death being one of bleak nothingness also must be reexamined.
The entire religion is a myth. It's a manmade religion because it was started by men and furthered by self-appointed leaders who set themselves up as God's...er...Jehovah's ministers. The Seventh Day Adventists and the churches of Christ were both started by people who believed deeply in what they were doing.
In Isaiah 11, the Millennium is being discussed. Then Isaiah writes: "And in that day there shall be a root of Jesse , which shall stand for an ensign of the people; to it shall the Gentiles seek: and his rest shall be glorious.And it shall come to pass in that day, that the Lord shall set his hand again the second time to recover the remnant of his people, which shall be left, from Assyria, and from Egypt, and from Pathros, and from Cush, and from Elam, and from Shinar, and from Hamath, and from the islands of the sea.And he shall set up an ensign for the nations, and shall assemble the outcasts of Israel, and gather together the dispersed of Judah from the four corners of the earth.The envy also of Ephraim shall depart, and the adversaries of Judah shall be cut off: Ephraim shall not envy Judah, and Judah shall not vex Ephraim."
Thus, before the Millennium can begin, this "root of Jesse" must appear and stand as an ensign. What is an ensign? It's a banner, or a standard to the gentiles, both Jew and gentile. And during this same time, the Lord would gather Judah back to the land of their fathers. If this root of Jesse has appeared, the trick is in finding him -- and whatever he is or teaches must be the truth. To say that Judah isn't gathering in fulfillment of prophecy is to deny what is before your very eyes. It began in 1896 and gained steam ever since. Thus, finding the root of Jesse must lead you to the correct course.
Think long and hard before destroying something your mother holds so dear. If you're determined to do it, then make sure you have a replacement for her that meets the same needs. If you don't, she'll never forgive you, and I wouldn't blame her. You don't kick the crutch out from under an old man without first giving him something better.
Just my two cents.