Dumb humans often don't notice when one of us is bullying another cat. They don't recognise what is going on.
So to help them, I am posting this this video showing a ginger cat bullying a tortoiseshell. What he is doing is pushing the tortoiseshell away from the owner who has the video.
There's no feline violence involved. Just a movement between the tortoiseshell and her human.
This is subtle bullying. The tortoiseshell needs her human to recognise this and see if she can help the cats avoid each other.
Seperate feeding bowls, three litter trays in three different locations, two cat flaps, lots of cat beds - so that the tortoiseshell can always get to what she wants.
And the owner should think of time spent with the tortoiseshell, when the ginger is not in the room and cannot interrupt.