Cat bullying

[Karen]

I am betting she is letting them know she is boss of them, and not to be trifled with. If there's no bloodshed, I'd not worry about it!

[Catsnclay]

We are going through something similar. We just contacted a cat behaviorist after 4 months of growling, hissing & loud screams. (I am/was ready to scream). The cat that is doing the hissing was mothering the kitten before he went on to be fixed. Strange, but we never encountered this before. She suggested we separate them for 4 days then re-introduce -SLOWLY- if there was any aggression then we had to start over. Well I'm excited to say that it worked.....for 2 1/2 days. It is somewhat tolerable but we will try again after Thanksgiving, there is just too much going on now.
So, it's worth the try, but you need to make sure they get along or start over.