I'm so sorry to hear that about your sister. My condolences. Can't imagine how frustrating it must've been, for someone to be so active, and suddenly not be able to. Though I do think being physically active is a valuable resource, one that (I imagine and hope) can power you even through illness.

Yes, I heartily recommend Shriver. She is frightfully intelligent and an extremely good novelist. She's the kind of writer who can piss me off how much I disagree with her (she's also a political/social commentator), yet I still have to admit it's usually a flawless write-up.
Her "Should We Stay or Should We go" is also terrific, as is (my personal favorite) "The Post-Birthday World". Really recommend both if you like the notion of alternate realities, and what-if moments.