Since about the time Spike died, our cat Bella became the...

Since about the time Spike died, our cat Bella became the-cat-who-lives-upstairs and refuses to come downstairs for any reason. We tried carrying her down there, feeding her down there, moving the litterbox down there (that really, really didn't work). It got worse when we got Tasha, who was kind of an angry kitten and immediately started to push Bella around, and took the opportunity to seize control of the downstairs. (Except for Harry. Harry's territory has no bounds. But he doesn't ...