This wasn't accidentally obtained. They stole a winning lottery ticket and didn't share the winnings.
There are 2 aspects here. One is about ethics and privacy, someone took and continues to use these cells with no restrictions, like saying it's OK to have a slave because it was legal when you bought it. What other things are perfectly normal to take because you have more?
The second is financial, you're expected to pay through your nose for using a 5s song snippet but use a piece of someone's body should only benefit the the ones who took it. Blood donors get paid and that's nowhere near as unique as this.
I've seen people rationalize the Tuskegee syphilis experiment (people get syphilis every day anyway). Were you in her place you'd expect more of everything. More rights, more respect, more privacy, more money, etc. And I don't see anyone trying to fix past mistakes.