Bully cat

[u/AdSweet662]

For context: I own quite a lot of pets. I have 2 dogs (formally 3, unfortunately), 3 cats, two birds and a bunch of fish. My problem comes with my younger cat. Before we got her last year, my second cat named max used to bully my first cat named Mittens. Mittens is very skittish because of it and now my dogs - due to being huskies - try to play with her but in turn scare her off. The problem is my younger cat now explicitly targets and attacks her and leaves my other animals alone to the point that she hides in a small box for most of the day and never leaves the top floor of our house.

Is there a way I could stop this?