Farewell my Mii-Cat

My Mii-Cat aka Lucymia died at the clinic today. After 13 years of being my most loyal little sidekick and the loveliest silly cat, she just suddenly died when we were so close to finding what was wrong with her.

I have a huge empty hole where my heart was only hours ago. My world just ended and it's name was Lucymia.

Here's what happened: after a surgery to remove plaque and unidentified masses, she first seemed to recover just fine. Then suddenly, after a few days, it went downhill.
My puffer fish had escaped from its tank and grazed Lucy. She didn't bite or scratch it, but I still worried about external venom, so I contacted puffer fish experts and emergency vet services. They all told me that captive freshwater puffers are not dangerous. So I let it go.

But she stopped eating, drinking, washing and sleeping in my bed with me. I took her to the vet who had removed those other things before. She told me that I needed to get rid of the new kitten, Orli-Pompom, because Lucy was just jealous/stressed/depressed.

But a depressed cat can walk. Lucy couldn't, so I took her to my friend's vet. On the way there, she had gotten much worse. When I took her out of the carrier, she walked in a circle, then collapsed. The vet didn't have the proper equipment and sent me to his colleague who runs a hyper-equipped clinic.
That vet then tested Lucy for FIV (feline Aids), did a blood screen etc., and for one, found a pneumonia. He also took x-rays because her kidney had enlarged all of a sudden and her lung wasn't good either. Also her heart was disrupted. Lucy had trouble breathing, so he put her in an oxygen tank.

I'm on bad terms with G-d so I asked my orthodox friend to pray for my Mii-Cat and he did. He must have blurted out my name, because the vet came out and told me he may have to resucitate any moment. And he did, he intubated and tried everything, but a moment later, he came back again and only said "I'm sorry".

I asked him to do a post-mortem exam to find out what took my lovely Mii-Cat from me but I think I knew it was the neurological form of FIP.

Update: The autopsy report stated that she died from a congenital heart condition.