

How do you say goodbye
I've had my cat for 17 years. Ever since she was only a couple weeks old.
We have lived so much life together, I got her right when I turned 16 after my dad passed away.
Now I'm 33, she has watched me become a wife, homeowner and mom. She's genuinely the best friend I've ever had. Even when I had absolutely no one I always had her, she means so much to me I could never begin to explain that.
That being said, recently I noticed she began to have a large abdomen, I brought her to the vet where they did an x ray and an in house ultra sound, it was not a formal ultrasound and it was performed by the vet not a radiologist. Still, she found what she believes to be a caviated liver mass and ascites in her abdomen. She suggested further testing was not needed and gave her a poor prognosis. Essentially she believes there is nothing that can be done to help her and recommended euthenasia.
I have been battling all week wondering if the diagnosis was wrong and looking at other alternatives.
I've called the vet back multiple times, she thinks wet fip is highly unlikely... She also believes draining the fluid may help give her relief temporarily but that it will fill back up and we will be back where we started.
The reason I am struggling is because she is still so much like herself.
She is still eating and drinking, she comes when I call her name and cuddles and purrs. She looks at me when I enter the room, she still can jump up and off the bed to use the bathroom although she has been pooping on the floor and wetting the bed more which I believe is due to the fluid buildup making it hard for her to get around.
I just don't know how I can say goodbye to her and euthenise her when she is still so alert and there, but her body is failing her.
Obviously I don't want her to get to a point where she is suffering, but I just can't bring myself to let her go either. This is the hardest thing I've ever faced. I genuinely don't know what to do.
I love her so much, at the end of this I want what's best for her. I do believe no matter what it seems as though she is at the end stages of her disease, and I can't magically heal her. But I just don't want to say goodbye to my girl. I'm so shattered. Please help with any advice