The first time I brought her home she will pee in my cat's sofa and she chase him.That is why I let her go.But last winter she was sick and pregnant so I decide give her a second chance. She had her kittens and she is spay and neuter. I tried the introduction and is not working. Now when he sees her he start chasing her.Sometimes they are sleeping ,one in one room and the other in the next room nothing happen but when they woke up and she start moving and sees him she start hizzing and he wants to chase her...As you say maybe one of them tried to be the alpha, and if that is the case how can i get them like each other. Oh by the way i used the feliway in plug in.