Older Cat Growls and Hisses at New Kitten?

My older female cat (approximately 1 year) has never been friendly to other house cats. We've had her since she was a kitten and she has been the only cat at the house apart from the strays my mom takes in. They stay only for a week or two (she is inside and the guest cats stay in a separate room outside the house). Recently we got a new male kitten, maybe a month or two old.

She hasn't attacked him yet, but whenever she gets even a little bit close to him she starts puffing out and hissing. The little kitten doesn't really mind her, he just stares at her like she is some crazy lady.
Both of them are fixed so I don't think it's a hormonal thing.

By Maria H.