My mom has gotten progressively more morbid these past couple of months - how can I help?

She’s only 66, but has been having some issues with her shoulder. (Possible surgery needed). Before that, she had an unexpected seizure, seemingly out of nowhere. (She had been under the weather for awhile.) Her neurology work-up came out fine, so they’re thinking it was just an atypical episode.

Thing is, she keeps on dropping lines here and there: “if this happens to me me: here’s what to do”. Once, she said she thought it was “all over.” Also, it not so many words, she simply implies that death is around the corner. She’s down in the dumps. So, I try to muster up my reserve and say complimentary, optimistic things to her. A few weeks ago, a friend of hers celebrated her 88th birthday; God bless her! So, my Mom was doing the old, ”I’m so old” routine today, so I gently reminded her that her clock hasn’t run out just yet, and jokingly said I’d have to deal with her for another 20 years. (Don’t worry, she took it well.) I said her friend was “proof-positive” that anyone can just keep-on-keepin’-on. Anyway, I’m running out of things in my arsenal to keep her going. Suggestions?