I would suggest that during the 4 weeks you have to keep her in you gradually mix a bit of shop bought compost with her litter
by the end of the 4 weeks aim to have it more compost than litter
then transfer that last litter tray contents to a part of the garden you want her to use - preferably one near the house, or under shelter if you want her to go out when it's raining, and if she uses it keep it topped up with compost, but gradually mix it up with garden soil
I also have an outdoor covered tray, sold by Zooplus, which I keep just outside the back door, and mine only use it when their garden patch gets waterlogged
but I also keep an indoor tray just in case - once or twice it has been used when the cats have had the runs, and as they probably wouldn't have made it outside I was glad of it