The four-time Emmy winner was diagnosed with lung cancer in 2009; in 2013, she was told she had a form of cancer that was affecting her brain, and was told she had three months to live. She bounced back, and even did Dancing With the Stars that same year.
As famous as she was for playing Rhoda Morgenstern on The Mary Tyler Moore Show and its spinoff Rhoda, she's also known for her contentious experience with NBC on the sitcom Valerie. She played Valerie Hogan, a married single mom (her husband was an airline pilot who was never around) to three sons, one of whom was played by Jason Bateman.
Harper quickly grew displeased with the show because the producers turned it into a family sitcom with wisecracking kids, which wasn't what she signed up for. She also had a dispute with production company Lorimar over her rightful share of the profits, and staged a walkout. NBC and Lorimar played hardball and fired her, and she sued and they countersued. Sandy Duncan was brought in as the new lead, and the show was retitled Valerie's Family and then The Hogan Family. Ultimately, Harper won a bigger share of the show's profits, although she took a hit to her reputation.
I had a kind of a crush on Valerie Harper when she was on the MTM show. I remember following the flap you describe surrounding her departure from Valerie but I never watched it. I remember, too, her cancer diagnoses and, frankly, was surprised to hear she lived until recently.
I saw a few episodes of Valerie fairly recently -- it was on one of those nostalgia TV channels -- and it was pretty mediocre fare. Which, I suppose, was the problem Valerie Harper had with it; the producers were turning it away from the vision she had for it, and she objected.
Here's a pretty comprehensive piece on the whole thing, from MacLeans in 2008: "The 20th Anniversary of the Most Awesomest TV Contract Dispute Ever". This situation is often painted as a greedy star demanding more money, but it's more than that; it's really a case of star standing up for her rights, and the network bent on crushing her it, to send a signal to other actors that this will happen to you too if you get too far out of line.
I also remember the very dire diagnosis Valerie Harper got in 2013; it got wall-to-wall coverage. But then, a few months later, she was on Dancing With the Stars, and I remember her on TV exulting at the turnaround in her health. Which was really great news. Dancing With the Stars is a hard physical workout for healthy people; I can't imagine doing that level of physical work when you're recovering from cancer treatment.
She was brave and strong. TV today was showing her on camera saying "don't go to the funeral until you're dead" or something like that. Good advice.