If you have a dog crate or x-pen, you can keep her in there with 2 litter boxes on opposite ends filled with hay on top of litter. Get her urine on a paper towel/newspaper and put that into each box. You could use just one box, but it usually helps to give her the choice of 2. She should be enticed to poop in at least one box while she eats. Her inclination to pee in it may not come right away, but the best strategy is to keep her confined during this process so you have a controlled environment where you can quickly clean up her messes in the areas you don't want her to do her business, so she understands the purpose of the boxes. Don't clean the box too well with cleaner in the beginning to avoid confusing her. Once she is peeing exclusively inside the litter box (some poop out of the box is to be expected), you can gradually give her a little more space to roam. Don't rush it and give too much freedom initially or you could undo all the progress. Keeping her outside will not help matters and will only stress her out as she is accustomed to being inside. If she is spayed when she comes of age, she'll be less inclined to mark everywhere. Hope that helps.
