I lost my cat and there’s so much I regret

A few months ago I noticed my cat had a cyst on her chest. I took her to multiple vets that tested the liquid and was told they were just cysts, that cancer was highly unlikely. I was told to remove them would cost upwards of $3500. I didn't have the money so there was nothing I could do immediately. But cysts aren’t that bad and I could save up in a couple of months. Cysts are rarely ever cancer. Right?

It took 5 months after I initially found the cyst to finally have the money to go to a vet that did surgery. I took her to the vet and based on the xray he said it’s cancer and it’s already spread, there’s nothing he can do. I’m sobbing at this point. I was too late, I took too long. There’s nothing I can do for her other than wait for her to die slowly. But at least she can go peacefully and I’ll have more time with her.
As a last resort the vet asks if he could do a blood test to see if there was any treatment he could do. I agree thinking it might be something to slow the cancer or to make sure she’s not in any pain.

I get a call later that the bloodwork showed the cancer hadn’t spread as much as he thought it had so he recommended surgery immediately. I took her in that week and she had a successful surgery. 2 weeks later she’s doing great but losing a lot of weight. Then week 3 she slowly stops eating. I do everything I can to get her to eat, the vet prescribes something to up her appetite. But she had lost so much weight so quickly. In the span of less than a week she looked skin and bones.

Then, she started having trouble breathing and I take her back in. The vet does an xray and sees that there’s liquid in her lungs. He says he thinks it’s either cancer or pneumonia. He couldn’t tell but will send the xray to a specialist. He says, if it’s cancer, she’s gonna die a painful death, unable to breathe, like drowning. I’m crying and ready to let her go. I didn’t want her to die in pain.

But he gives me false hope, says if it’s pneumonia and he starts treatment now she might make it. That this might just be unrelated to the cancer. Says he’ll send her home with medicine and breathing treatments. I was really unsure but seeing her feeling better after a breathing treatment, I believed him.
I took her home and she seemed to get better, for one day. She was so upset to do the breathing treatment but I thought it was helping her. I was confused why she kept trying take the mask off if it was helping her breathe. The next day I try to give her the medicine but she spits it back up and starts panting, I try to give her the breathing treatment but she’s just getting worse so I rush her to the vet, I wish I didn’t. I wish I had stayed at home with her.
When I got to the vet she’s meowing in fear, panting and coughing. They take her back immediately to put her on oxygen while I wait. It’s so early I’m the only one there. 5 minutes later they come back out and say she died. She died panicking, in fear and unable to breathe. I let her last moments be with strangers while she meowed in fear. When they brought her body in her tail was still puffed up in fear. The vet told me he had just got the results back for the xray and the cancer had metastasized to her lungs.

I regret it. I regret it so much. If I had just waited a few more minutes she could’ve passed at home, in my arms. At least with someone she loved and trusted.
If only I had told the vet to put her down when the xray showed her lungs were filled. She would’ve gone peacefully rather than like she was drowning.
If only I hadn’t done the surgery she would probably still be alive. She would’ve still died but it could’ve taken a whole year. The cancer wasn’t hurting her, she was still lively and active before the surgery. She still had life left to live.

Or if only I had bit the bullet and borrowed the $3500 and had the surgery months ago.

Even more absurd, if only I hadn’t gotten her when she was 2 years old already. She had breast cancer and I learned that the earlier a cat is spayed the less likely they are to get breast cancer. All the way until 2 years old where spaying no longer has any impact on developing breast cancer. If only she had been picked up by the shelter sooner. If only she had been spayed sooner. 91% less likely to develop breast cancer if spayed at 6 months.

I imagine finding her when she’s a kitten, taking her off the streets even though I have no idea of her life before the shelter. Only that it took a long time and a lot of trust building for her to no longer run at the sight of a person walking towards her.
I imagine I get so many more years with her.

I remember when I first saw her at the shelter. I knew immediately she was perfect. So soft and beautiful. So sweet and affectionate. I will never have another cat like her.
All her quirks and personality, all the time we spent together, all the things we learned about each other, all our conflicts as well.

Like when she’d get angry at me for a few hours after a vet visit but forgive me after I fed her treats and she’d tell me she was still angry by “accidentally“ nipping my fingers when eating treats out of my hand. I knew she’d forgive me when she no longer nipped at my fingers. How she forced me to become a back sleeper because she loved to sleep on my lap but would abandon me during summer because it was too hot. How when I first got her she would wake me up hours before my alarm by putting her paw on my lips to let me know she wanted to be fed. Which led me to be a staunch supporter of feeding only at night (wet food, dry was always available bc she was good at free feeding).

How I would greet her with a head bump and a kiss everyday. How she would never scratch or bite. How she would let me hold her and pet her more than anyone else but still loved people giving her attention. How she loved to sleep under blankets and when I slept on my side she would sleep in the crook of my arm. How she always asked politely for food from my plate and wouldn’t eat any human food unless held for her. How she had pollen allergies like I do, I couldn’t open the widows during spring or fall. But she loved to look out the window for hours on end.

I miss her. I still see her limp body in my arms when I close my eyes, hoping she’d start breathing again. That I could take her home in her carrier and she’d gain all her weight back, she’d get better and I’d have more years with her. But I’ll never hug her again. I’ll never pet her soft fur. She’ll never lay on my lap again.