Oh what a horrible response....
That said, given her age, and the very high probability of depression in elderly people, it might be kindest to give her a second chance.
"Grandma, you sounded very hurt about our gift, and I hate that you felt that way. We did not mean for you to feel badly. How about we come take you to lunch/dinner/brunch and enjoy a nice time out together?"
It's not an apology, but she could be having emotional/mental issues from either physical issues (dementia, which includes but is not limited to Alzheimer's) or medication side effects.
At her age you really are not going to be having many more opportunities for her to be snarky.
My elderly aunt who passed away last spring could be quite rude when she wasn't feeling well. She snapped at another resident of her facility horribly once, and then cried later over it.
Perhaps it is time to treat her as you would a very small child...with extra patience that she is perhaps overwhelmed with many issues.
The rest of the family, of course, gets no such pass/excuse.