Help stray kitten with broken tail

Piglet/piggy has an open wound when her tail broke. She is less than a year old and living with open wound since i have seen her. She was taken to vet earlier this year and was told she might gotten stuck somewhere and broken her tail and skin. Vet said there is healing issue so should heal itself but now Piglet’s wound is looking very red and irritated. SPCA refused to chip in towards the surgery. Piggy is raised by a stray cat couple and bonded with them. I do not have heart to separate them and give her to any rescue. Piggy used to look very scared and run away everytime she saw a human and now gaining her confidence back. Vet has given an estimate quote of $803 to fix her tail wound. I cannot afford the whole amount by myself. Piggy and i will be very grateful to any help to put towards her surgery.