I have a 21 week old Himalayan kitten. NuNu is her name. My friend just a male himalayan, Cyrus is his name.
I had NuNu spayed 3 weeks ago. We have introduced them last Sat. My friend and I live in the same apartment complex. We would like for our kittens to be playmates, but NuNu seems to hissing and growling a lot when he comes to visit.
I know she is protecting her territory. His kitten is 12 weeks old.
Last night I had them both, NuNu hissed and growled a lot, but after a while, she would chase him around the apartment, then he would chase her, then they would hiss at each other. Is this their way of playing?
Is there anything else we can do to help them like each other?

I would let them visit daily if possible. At least until they get used to one another. Also trying giving them cat treats, but only when they are visiting each other also sit and stroke their fur. I think they will be just fine with each other after awhile.

Most female cats behave this way especially after being spayed.Your cat is showing her dominance over the younger cat.She may eventually change her behavior,but her hormones are screwed up and she is letting this male kitten know who is in charge.
BushG. Is right,give them time,I think she will come around.:)