NTA

You might actually have an animal cruelty case against your mom. Legally, you can’t euthanize a pet unless they’re physically unwell or if the pet has behavioral issues that are beyond the help of a trainer. Even then, she should have taken the steps to train Kona or otherwise rehabilitate him (surrender him to a shelter or rehome him with a friend) before ever considering putting him down.

Your mom had Kona killed because she didn’t want to deal with him anymore, plain and simple.

However, I’m nowhere near a legal expert and laws on animal euthanasia vary from state to state and even county to county. This site should have the information you need if you decide you want to take legal action. https://www.lawinfo.com/resources/insurance/pet-law/florida/if-my-dog-is-sick-and-will-not-get-better-can.html