Katie i know it is the better option to keep the cats indoors, but in NZ it is the norm to have indoor/outdoor cats as all my four are, i always keep them in at night times,this probably is your best bet, and don't worry she will be fine, you could restrict where she stays at night time, in a bathroom, and hopefully she will do most of her peeing outdoors,honestly if everything else you try fails, then make her an indoor/outdoor kitty,it really isn't so bad, hundreds of kiwi cats live this way very happily,(infact you are hard pressed to find an indoor kitty here except where they are used for breeding) of course we don't have the same predators that you do in the USA, and that is always a concern.