We adopted two cats together, a brother and a sister, about a year and a half ago from a rescue organization. They are both spayed / neutered and are probably about 1 year 8 months old. The sister is ~ 2lbs lighter than her brother
About six months ago we noticed that when they would play the female cat would begin hissing, yowling, and taking swipes at him. Sometimes this happens because the male cat is harassing her - chasing her around, biting at her heels a bit when she runs away until we separate them. But it also happens when she instigates and it seems like they're playing normally.
There's never any 'puffing up' or back arching, but she's clearly upset and claws at him to get him to back off.
Recently we came home after about four days away (we had a cat sitter visit daily for a couple hours, but they obviously weren't getting as much attention as when we're home full time) and found that the male cat had a small scratch by his ear, so it seems like it has escalated.
Does anyone know why she's getting so upset? Is hissing normal during play?
Also, is our stopping the male cat from chasing his sister inadvertently encouraging him to continue doing it, since he gets attention for it? If so, how can we make sure she feels safe without giving him attention?