It can take time to get 2 cats/kittens to make friends, or even tolerate each other x It's hard on both parties as obviously your girl has been at yours longer she'll now feel she has to share you which will be the main reason for not liking him so much xx

try to find positive things to do with them, like using treats or toys - maybe also a feliway plug in or two round the house to help promote a sense of calm x

they may not ever be the best of friends but they can certainly learn to find harmony with each other, just remember to give your girl as much fuss as always just to make sure she knows she is still your beautiful girl and that having another cat won't change that xx

good luck and hope everything settles nicely xx

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