I had to do the same thing a few years ago, Herc. The new third kitty was starting fights and finally when she attacked my Valentine's Day dozen roses vase, I lost control and spanked her. I had to take her back to the humane society that day, Valentine's Day, and tell them to get her a home where she is the only cat. When we were alone, she was wonderful, but when she had to share me with two others, she fought them and drew lots of blood. I cried and cried all day.