Phantom’s feline infectious peritonitis treatment

Hello, my name is Kaila and I am fundraising for my cat Phantom. She is only 1 years old and is a beautiful Maine coon. She is our family cat that both me and my little boy love to pieces and she means the world to both of us. We have had some animal loses in our family in the last few years and really do not want another if we can help it. She started showing some strange symptoms like her belly being swollen so I took her to the vets today and they have ran some tests and told me she has feline infectious peritonitis which is a form of the coronavirus. She is needing 12 weeks of treatment which I am struggling to afford and if I can’t afford it I will have to put her to sleep which I really do not want to do. It will break mine and my little boys hearts. Any help is appreciated. Many thanks for reading everyone.