Knittingnancy, I, too, am sorry for what you are facing. Like pps, I'm also wondering if this estrangement is really about a chair. It feels as if there must be something else going on here. Is it possible you broke a rule dd has for her kids and that's what this was about? Did it happen before, so that maybe this was a "last straw?" Since it sounds as if the event was in your house, I think you should have been able to make your own decision, but, maybe, dd doesn't see it that way?
Regardless, since she said, sadly, that you have "lost" her, I don't agree with continuing to send her cards, etc. I'm afraid she'll just see them as you dismissing what she said. I do agree that you should continue to send them to the gc, except perhaps the one who sent you that "nasty" message. Your decision, of course, but I don't think she'll appreciate them.
Meanwhile, I'm sorry you're stuck indoors so much due to your disability. Is it possible to hire a health aid who can take you outdoors, sometimes, etc? I know you have dh, but he needs a break, too, sometimes, I'm sure. And an aid could increase the amount of time you got to get out and enjoy.