Regressing?

My cat Maggie, one year old spayed female, and I got new roommates at the beginning of July. Serah, my roommates kitty is also a one year old spayed female. After just a couple of days, they seemed to really hit it off. Not best friends, but definitely companions and play mates. We were so grateful that they took to one another.

I took Maggie with me to my parents this past weekend and when I brought her home, Serah acted like she doesn't even know who she is. She's hissing and growling and just being mean. Maggie just lays there like she could care less, but it's bugging me. Does she smell different or what else would be the cause of Serah's reaction? I'd love any input or suggestions about this.

Yes! Maggie came back with all kinds of new smells. Since cats identify each other primarily by smell Serah is confused and thinks that Maggie is someone new. It shouldn't take too long before Maggie's normal smell returns. In the meantime, you can get a slightly damp towel and rub down Serah, making sure to rub her cheeks and base of her tail. Then use the same towel to rub Maggie. This will transfer Serah's smell to Maggie.

.I agree with lotsocats Maggie has come back with strange smells attached to her.
The idea of the towel is a great one I have had to use a similar technique before, you may also want to try taking a rug or jumper that Serah has been sleeping on and rubbing it on Maggie .
That will also help restore the familiarity

Best of Luck

Tish