How do I handle this?

It's a crappy situation, you did the best you could. You can't afford to replace the carpet, and you had no idea they would do that to the dog. It's common in shelters, especially if they don't have the room or means to take care of the dog. It isn't your fault, she is just upset. Apologize to her for bringing the abortion up. She is just angry, give her space give her time. This is how sisters can be sometimes.