Once they get the taste of blood in their mouth, the thrill of the hunt, the rush of the kill...
Nothing to do but put them down.
Putting animals down because they are old, in pain and can’t eat is different than putting them down because you suck as a trainer.
I’ve NEVER murdered any living creature (oh, and I have trained horses, cats and dogs). What she described is no surprise. She literally trained Cricket to kill birds and is upset because it did as she trained it.
She sucks as a human being.