This may sound icky, but take some of her poo and a paper towel soaked with her pee, and leave it out in the backyard. Take her out the next time she's due (try to place her close to the poo and pee) and wait as long as it takes this one time for her to do her business. Once she does it, praise her highly. It might take a few more times of this, but your main concern right now is to get her to appreciate the backyard as her toilet. It gets easier from there on (not that you won't still have accidents every once in a while). Good luck!!!