Man, the sad thing is, I truly think the sister honestly believed that was the right thing to say at that moment. She honestly thought that would cheer her up. I think the saying is nonsense, but you can say that after you don't get the job you initially wanted, only to get a different one that you enjoy better two weeks later. Or maybe when your plans to sleep with a female fell threw because you had other arrangements, but you dodged a bullet because it turns out the chick had the clap. You don't say that after someone gets told they're a few months away from death.
But yeah, cancer is a beast. Doesn't discriminate based on age or status....can hit you at any moment. My ex had a friend that she kept in constant contact with after HS. Last they spoke, everything seemed normal, but my ex hadn't from her in over 90 days. She gets a call from the chicks parents telling her the girls three states over undergoing heavy cancer treatment. She's only 22 and the ex hasn't heard from her or her parents since, so we don't even know if the girl is alive or dead. Really have to appreciate good health, man. It's absolutely chilling at how fleeting it can be.