I'm sorry to hear this but unfortunately I don't have any advice to offer you either. When I still had my Pepper, Storm began attacking him because he wanted to play and Pepper just wasn't interested any more. They had been best friends too. This is when I decided to get a 3rd cat,Sunny, so that Storm could have a new playmate. I won't say that this would work for you but it did work for me. Hopefully things will improve with time. Good luck.