Don't just leave her outside...actually go out there and make her do her business. If she doesn't do it, walk inside, then take her right back out. Do this until she goes. When she goes, throw the biggest party you can think of. Do this over and over again until she gets that she's supposed to go outside. It's also possible to hang a bell on the door...ring the bell before each time you go outside to make her potty, after a while they get a hang of the fact that if they ring the bell, they go outside, and get to potty. It's very useful for a puppy that can't hold their bladder for extended periods of time.
CD RE TC HIC 7/10