Hi so basically I’ve been looking for this for a while now. Basically the story is about a girl who somehow gets into an alternate world where cat and dogs run the place and humans are the pets. She’s brought by this one cat guy and I think he used to be her cat in the real world I’m not sure. She also meet this other human girl but the other girl wasn’t a pet and like had to work instead. So if you know what I’m talking about please help.

I know of a manga that's similar, but instead of a cat, it was a dog. She also, during one chapter, meets another human who is a pet of another animal. It was called Kainushi Juujin to Pet Joshikousei however, again, it was a dog and not a cat. Still, a lot of the rest was the same as you described.

I'm a jack of all trades but master of none. Too many jars and not enough hands.

Searched the "Human Pet/s" category and A World Ruled by Cats was the first result. Could this be it?

~4400 manga completed
~1700 ongoing...