We adopted Tabby sisters early this year, and they are now both a year and a half old. They are both spayed. Lately Sheena, the larger cat, has taken to bullying the smaller built cat, Zoey. Sometimes they will fight, and Zoey will cry out in pain from being hurt. I read some things online about sibling rivalry and tried giving them separate eating and water dishes, and we got a second litter box. It seems that Sheena is using both litter boxes. When I feed them wet food in the morning, Sheena will actually leave half of hers uneaten to hurry over and take Zoey's food. Zoey is always looking over her shoulder when eating. I tried putting her in a separate room with the door shut and she ate, but when I let her out, Sheena started bullying and attacking her. They also fight on my bed, since they both like to sleep on it at night. I applied a Pheromone spray on the blanket and that seems to help at night, at least. There is a tall cat condo in the living room and a good scratching post in the dining room. They also have two cardboard scratching posts and one more stand up post upstairs.
I am at my wits' end about the fighting; I can't stand to see an animal getting hurt. Any suggestions?