Raising money for my sister cat surgery

My sister got a cat from humain society and it had a cut on it and they told my sister it would heal but. It has not and now the cat needs surgery and its only 2 years old female cat. At the vet she took the cat to, the vet told her it would be 900 for a surgery because they have to cut away at the dead skin and give it medication after the surgery. Any type of donation would be grateful to help save my sisters cat the surgery will be on june 19 the money will need to be in by. Thank you for anything.