Cats are territorial so don t be surprised if the new cat gets an inhospitable greeting.
This will help to prevent your cat from holding you responsible for this intrusion. The new cat should be brought into a room set up for this purpose with her necessities. Allow your cat to check out the newcomer while she is still in the carrier. Be prepared for some complaining. After your cat has finished checking out the new one in this way, remove him from the room and distract him with a treat or special attention.