Its so unexpected, she was 100% the night before.
That's what happened to my dog last year. My sister in law was watching him for one night, and the next morning I got a tearful phone call. That one hit me hard. I'm still kinda reeling from it.
They say that our animal friends are some of the hardest to lose, and they're not wrong. I also know I make a lot of anti-cat rhetoric, but in all honesty, I'm sorry for your loss.