my cat was never mean to us. she was the sweetest ragdoll ever. but we brought this kitty home for her and she hates him she growls and hisses. we didnt put them together but only through a crack in the door. how to i introduce them correctly? i know thorugh a crack in the door, his own litter and food...but any other tips? thanks! my cat is 6 months this kitty is 8 weeks.