While consciousness and feelings are intangible things, the physical structure of the emotional centers in the brains of cats and humans are similar, and contrary to stereotype cats are social animals. So it is highly likely that Ratsie Katsie is having grieving feelings we humans would easily recognize if we could somehow hook up a jumper cable and share in feeling her emotions.
Pam has a lot of good info on and experience with cats.
This might be relevant and helpful,
https://www.wayofcats.com/blog/dear-...epressed/14782