hmm.. i would say try the sticky paw things, or vinegar on the door... but you mainly gotta figure out what makes her do it..lonely? hungry? etc...

My cats only do this when the doors are closed and they want in.. And now i don't have to let them in either... Eliza will actually OPEN the door (and we have full knobs, not a pull down handle) and let them all in LOL thank goodness for bathroom locks!