it sounds like she's very territorial and you're her territory. as long as she gets your attention she'll obey you, but you won't be able to pussy-foot (i know - bad pun) forever.
you could try the old perfume trick. i used to introduce new kittens to the old ones this way: spray myself with perfume - the same one for a few days. cuddle the old cats until they associated me with the new smell. rub the scent on the new kitten. they associated the new kitten with me and accepted it.
what if you tried that and applied the scent to/around the litter pan? any thoughts on the subject, anyone?