I don't agree with my wife's decision to pay $2500 for my step-daughter's dog's surgery. I think it should be allowed to die naturally
That's a big bill, but it's her pet. Why are you against the surgery?
It just makes me furious. She doesn't know how to handle finances like I do.
I think that wanting to make your dog have a surgery instead of letting them suffer is a very noble and humane thing to do, but they also need to think about the expenses and if they can afford with moving forward with surgery. I would recommend that you speak with your wife to possibly talk about the ways how you can also humanely put down the dog and not spend a fortune towards the surgery.
You don't get it. She's not humane or noble. She's spoiled and doesn't care about the money.
Just because she disagrees with your opinion about how to handle a sick dog doesn't make her spoiled. Maybe she cares about the money but she loves the dog enough that she thinks it's worth the bill. You need to talk to her about it and base your decision on what's best for the dog and what you can safely afford, not how you feel about your disagreement.