Why is my female cat acting like she doesn't remember my male cat?

by Kanai
(Iowa)

My male cat, Frank, loves to go outside. My female cat, Asia, does not, so she just stays inside and watches.

Usually, I'll carry him around for a little bit and bring him back inside and the cats go about their days as usual, playing, sleeping, and eating.

However, I recently bought him a leash and harness so he can walk around a bit, but now when he comes back inside, Asia is acting like he's a cat shes never met before. She starts hissing at him, but not attacking. After a few hours of her being alone, she comes back around and they act how they usually do.

I would love to know if there is a way to avoid the first stage when she is acting aggressively towards him. I don't want either of them to be stressed out. I don't want to stop taking Frank outside since he LOVES it!

I want both of them to be happy and live in a stress-free environment. Any advice would be very appreciated!