If you want to look more "feminine," use the human concepts. You could add big eyelashes to your costume. Put on a pink collar (although I love the color pink and wear it often, I don't have a pink leather collar (interesting idea I had there!) and I'm a male). You could wear a bra and panties on the outside, maybe with paw-prints on the breast and butt. That would be cute!
Look at the muscial CATS (It's available on tape.) There are a number of female cats that express their femininity in different ways. If you want to be an authentic female cat, some of the characteristics they use might help.
Have fun! Halloween is for fun! BalletMaster[/i]