My family recently welcomed a new kitten into our family, her name is Callie and she is approximately 4 months old. Now, it took Brooklyn about two weeks to get friendly with Callie and they were INSEPARABLE after that. Now? Brooklyn hisses, slaps, and runs after Callie for anything and everything. What could be wrong? Is it because Callie isn't spayed yet? Callie is terrified of Brooklyn now and is very hesitant to walk by her and when Brooklyn gets to her, she becomes immobilized. It's frustrating. I want them to act like sisters again.