We have a Yorkie, Lexie, who is 18 months old and us usually fairly well behaved. (SitStayFetch has been a godsend to us in raising her, especially the Alpha Dog tips.) We also have a cat that we have had for 4 years, Tasha. Lots of times the two of them play together, chasing each other, hiding and jumping out etc. But as Lexie has gotten older she is sometimes very territorial toward our cat, many times not allowing her to come in some rooms or chasing her out quite fierciously nipping at her heels. And heaven help us if the cat gets too close to anything that Lexie considers hers, including food, toys, treat etc. She does not react that way toward us when we approach her so I think she considers herself superior to the cat but not to us.
We have tried reprimanding her, putting her in time out (in her kennel) until she calms down, keeping her on leash and stopping her forceably, and even keeping them in separate rooms. I know that I am missing some step that I need to implement to stop this before it gets worse but I am at a loss to know what to do. Can anyone make any suggestions please?