I can do you one better: My dad's will states that when and if he dies his body is to be donated to scientific research. Why? Won't Jehovah be doing away with any maladies that such scientific research would help to treat and prevent? His body will be donated specifically to cancer research since he had 4th stage throat cancer, was not expected to live, and survived with a combination of non-traditional and traditional medicine with an extremely heavy leaning toward the non-traditional medicine. The doctors are interested in studying his body after he dies for this reason. But, again, won't Jehovah be eliminating cancer well before the doctors could really benefit from anything they learned from studying him?
I recommend you do what I do: don't mention the incongruity between their acts and their beliefs. It would only prevent my dad from doing some good that is important to him. And in your case it might prevent your mom from doing something beneficial for her future. If they feel their actions are 'stumbling' us it will not make them question their beliefs, it will make them question whether or not they should continue on a course that makes us think they don't believe and therefore may dissuade us from coming back.
I would love to believe that my dad's actions mean that he has doubts, but I've just seen him do too many other things that convince me he still believes, and believes devoutly, that he has the truth. I won't lie to him about what I believe. I see no reason to lie to myself about what he believes. I gave up on false hopes a long time ago. If I was going to hope for something that wasn't true I would still believe in the paradise earth, not that my dad might secretly be harboring doubts when I know he isn't. These days I would rather hope for things like my niece making the cheerleading team because it's important to her or my grandparents selling their house quickly so they can move into something more managable for them where I won't have to worry every time I take them grocery shopping that my grandma is going to fall down the stairs just trying to get to the car or hoping that neither of my parents' cancer recurs or hope that my nephews are always as excited to see Aunt Jackie as they are now {though that's probably a false hope, too, little boys do grow up ;) } or hoping that the weather is beautiful in May so I can take all my nieces and nephews to Grant's Farm and the St. Louis Zoo. There are just so many better things to hope for that actually may come to fruition for me to waste time and energy on something that will ultimately disappoint me when it turns out not to be.
Don't get me wrong, I would be ecstatic if my dad ever got out. But being realistic I know that at this point it's exceedingly unlikely and there are just better things to focus on these days than worrying about what my dad does or does not believe. What a beautiful life it is. :)
Jackie