First off, thank you for taking in and fostering this little guy. And for helping him with his issues so he can find a great forever home. I think you did the right thing in kicking out the girl who throw him. She's lucky you didn't call the cops (or punch her in the nose!). But it might be best to find a new room mate. What if she brings her daughter in when you're not there? I am concerned not only about Rocco, but your other babies as well. I'm worried they'll retaliate as well.
