Harsh reality. How do I support her without getting hurt?

I love thrift stores and usually find boxes of vintage postcards, notecards, etc. If you read something and find an inspiring quote, jot it down and drop one in the mail to her.

You can always call her. Make sure you have positive stuff in your mind to yak about and don't let her go down any negative or dark rabbit holes. If she starts to get negative or nasty you can end the call quickly with "Gotta go, Gramma, I'll call you again soon."

I am all with the suggestion of nice cards. Perhaps a nice gift of candy here and there. Flowers. Anything. I would also be up for a visit myself, but I would be very ready with the "Seems you aren't having a very good day, hon, so I am going to be on my way. I hope all goes well for you. I will be back soon".
The trick is, I guess, to do the new "stone thing"--is it "grey rock" when it all goes south, but I strap on running shoes then as well.

Cards, send cards!! My mom loves to get "real mail", and my one cousin and his wife send a card about once a month.. she loves it, saves them all! They have lovely ones at the dang dollar store even,, two for a dollar! Put a little note in there about what you are doing, or a picture of your self, or a pet.. Maybe a little "care package" of treats and puzzles and such.. every other month or so? Snack foods and the like. Something to brighten her day.