I just moved in to a new place with my girlfriend, and we moved our cats in together. They both like to occasionally play, whether with us or with toys.
The bigger, older cat really likes to play with other cats, but when he pounces on or chases the younger, smaller cat, she hisses, yowls, and gets very aggressive body language.
They've never seriously hurt each other, and are completely comfortable around each other when the order cat is not excited.
Is there anything besides time that may make the younger cat realize that the older cat is just trying to play?