Don't go too far. Just rememeber, it's for her, not you. It's hard to do that sometimes.

Just remember at this point that you're likely to experience a flood of regrets: "I didn't spend enough time with her", "Maybe I could've saved her if I [convoluted, long-shot scheme you had no way of thinking of]", "I treated her too harshly", "I didn't give her a good enough life in some way", etc.

Discounting the possibility out of hand you have some serious skeletons in your closet, none of this is true. You'll want to feel agency over a situation you couldn't possibly have controlled to any meaningful extent, and when the inevitable is in sight, the only way you may see to express that is to look backward – and when you didn't do anything wrong, you have to make it that way.

If you experience that, what you might not see in the moment – looking at a present you have minimal control over and a bygone past – is that there is another direction to look. You can look toward the future – to honoring the love, comfort, and companionship she gave your life and sharing that with and finding that in the pets and people in your life going forward.

She knows she's lucky, and she knows you're lucky for having had her. You did a good job.

Feel hugged and have my sympathy
Went through something very similar and it's hard to lose a precious soul in ones live

Make the best out of the time you have left

I tried to tell my cat everything, I wanted to tell him. About stuff we experienced together and things that I'm sorry about.
I'm really glad I did that and although it still didn't feel enough, it helped.

Wish you two the best

cats are prone to cardiomyopathy, aka genetic enlarged heart, seems to be common in most breeds. except the rare ones.

She is a beautiful sweetheart and I can see how well loved she is. It sucks watching them get old. I lost my soul kitty a while ago and will think about him every day forever. Much love to you both 💕❤️💕