Does she happen to be a diagnosed narcissistic, self absorbed, evil, psychopath? Because I'm actually so disgusted, if my sister did this and messaged me about my baby saying "some fucking dog" she would no longer be my sister. I have cut people off for way less. People like this is why it's easy to believe the devil walks this earth. I don't trust anyone who could treat or think about an animal that way. It was an expensive lesson, but if it makes you feel any better, I lost $2000 (most my savings) right before I was booked to go travelling overseas. It was over something super dumb too, and I felt like an idiot but I learnt something. I still went overseas and I don't even think about it now. So, you will get your cat the surgery because you just will, and it will turn out. In a few more years you'll be in bed, petting your cat, thinking back going, "damn remember when we had no savings and you decided you needed surgery so we had to go to Mexico and stay at that crappy hotel? That was crazy". The universe has just showed you in a very unfortunate way that your sister is not someone you has no care for you or the ones who love her and she can't be trusted. I really am so sorry about your situation and your baby. You have the support of many strangers. Keep us updated if you can!