That is a horrible story, he needs to threaten her with a call to the police, as what she did is illegal for multiple reasons, thats theft, animal cruelty, and possibly release of a non native species, she could go to jail for that! Maybe after he threatens her with legal action she will admit what she actually did with it...

If my girlfriend did this I would go absolutely ballistic! I would probably end up in jail myself after the way I would respond to this.

How could someone do that to someones pet! and then refuse to tell them what happened! Would she sell her baby to gypsies if she didnt like it anymore? As far as I am concerned what she did is on almost the same level as that.