This is what I've had good luck with:
-Keeping her crated when she can't be with you, even if you're home
-Keeping a leash on her while you are with her, even in the house
- going outside with regularity, starting with every 1/2 hour to hour and graduate to longer periods of time between going outside.
- when you're outside tell her "go potty", keep telling her until she goes. When she does go give her a lot of praise and a small treat.

Good Luck!