I too was naïve enough to think that since my girl was shy around people I needed to solve that by getting her a companion. I wasn't aware growling was something cats did until making that mistake. It's especially weird because I don't think I ever heard her hiss. Her growl was very intimidating to me, but not to the kitten. Okay little man, I'm not sure she wants to play today.

I think she was mad about that decision for a long time.