so very sorry for your loss, I know what you are going thru, as does Muffin understand what your other kitty is feeling! I lost a cat earlier this year, and I still miss her, Muffin missed her alot too.
there is a thread called pet loss links, you might want to read that, if you can't find it, let me know and I will send the links to you.

what happend to your kitty? how old ?