This is kinda a mix between 2 methods I heard of. From the HS, and from a show.

When you catch your dog doing it's 'thing' inside, make a distracting noice (not to scare it) and take it right outside where it's suppost to go.
Another thing you can do, if she's paper trained, is to take a little of the paper your using for her to go on, and put it outside on the grass or whatever, and gradually work your way smaller.

Zeke, my new pup, knows he's suppost to go outside too. He only pee's inside from time to time now. I think it's just cause he can't hold it sometimes, and he's not completely house broken. I just take him outside a lot, like, ever few hours, and right before I go to bed. When he goes his thing, I make a big deal and say how good he is, (maybe a treat too?) Eventually your dog will understand, when she pee's inside, it's not good, cause you take her right out, and maybe said no too, so thats not good. But when she pee's outside, your happy with her and she gets lots of attention for it.