“For four days I did volunteer work for someone who owns over 100 exotic cats. I found the conditions deplorable and contacted an organization they belong to. They realized I was the one who did this, and harrassed me on the phone, accusing me of being from an animal right’s group. My question is this: Can these people sue me for describing the conditions of their place to the founder/president of the organization they belong to (an organization for cat breeders)?”
Your first call should have been to the local police department reporting her for inhumane treatment of animals, which is a crime in most jurisdictions. Notifying the cat breeders’ association may also be relevant, but protecting the lives and health of the cats is the moral imperative at work here, not getting her in trouble with cat fanciers. So please make sure you have your moral and ethical compass correctly tuned in this matter.
In any event, the main claim she might have against you is defamation (in spoken form, it’s called “slander”). But truth is always a defense to a claim of defamation. She could also claim that you breached some sort of confidence, but since you were a volunteer and she presumably invited you into her home, she would have a difficult time proving that you owed her some duty to keep her affairs private, especially if she is potentially engaged in criminal abuse of animals.