That's a sad story, I found most people in my old congregation more genuine than that, I guess it all depends on the type of people, usually the congregation announced things like that, "so and so is in the hospital and is accepting visitors." - makes me sad to know not enough people made the effort to come and see your mom.
I agree with Gopher and I can't say it better so..
"You did the right thing in DA'ing from the congregation, and it sounds like your mother well understands why."
It's nice to have support from your family members.