Who am I to play God? But who am I not to provide the compassion of death
over suffering? But there might not be any suffering. But there already is
suffering!

If this were my cat, I would call your sister and set an appt to administer the
shot at home. I would make the best meal in the world for your little kitty,
even things that are bad for her like tuna in oil and fancy feast. I'd let her
eat, I'd pet her all she likes then when she has her after meal nap, I'd give
her the shot to let her die mercifcully with dignity. If you let her get worse,
she and you will feel bad and have horrible last memories. If I'd known about
my cat's horrible cancer, I would have made him a great meal a few days before
he showed any signs. I would have played with him all he wanted, pet him...then
let him go to sleep while he was feeling good and happy. My prayers are with
you both.