From what I understand about her arthritis, she also has TMJ, which is a type of arthritic condition that affects the jaw. Doubt she used her mouth to play bass and guitar

But she was able to resume playing when she started taking glucosamine. So this tells me she had a susceptability toward arthritis anyway. I don't know what initially caused her arthritis and TMJ, but if it was totally based on her playing, she surely would have developed it in the 60's when she was playing 16 hour studio days every day for years.
Not sure how that's applicable to this discussion, though. It's not like this method of using a pick doesn't work just because she had a bout with arthritis.