I really swear by the baby powder trick. Sprinkle some in all the corners and going in and out of the closets. You can also try the pennies trick, but I think with a cat around you'll have an easier time with the baby powder.

And just keep looking. Ball pythons don't move in a way that really triggers the prey instinct of other pets. But I have dogs, and we all know cats ain't dogs, so it's better to locate her and get her safely back in her tank rather than worry about the possibility.