We have two female cats (both not fixed) that just DON'T get along. The cat we got second just picks fights left and right with the first cat. I had to put the bully cat on the patio (enclosed) today just so the other one could get a good play in and eat without looking over her back or hiding in something. They will use the same cat box, but wont eat from the same dish.
The first cat has not had a good play in for days, today she is just running around having fun since I have put bully cat on the patio