Help Cali survive FIP

My rescue cat Cali has FIP, Feline infectious peritonitis. This disease used to be a death sentence, but in recent years a treatment called GS has been developed that has already cured thousands of cats from FIP. The treatment is expensive and has to be injected daily for 3 months. Cali still needs vet visits for blood tests often along the way as well. We are asking for any help, we have already spent over $1000 on vet visits alone for Cali in the month and a half we have had her and the cost will continue rising. She is a beautiful cat, so loving to us and she will follow wherever we go. We thought she was a kitten but have since found out she is 6 or 7 years old. She was starving when we caught her outside, and we were able to contact her old owner through a rabies tag on her. He said he gave her away a while ago when he moved but had no other information for us and has not returned our calls since that first day. Thinking of someone having an animal for so many years and then leaving her behind breaks my heart, I want Cali to have the life she deserves and she cannot do that without first surviving FIP.