Welcome, Sally!!!
How wonderful you opened your home to another kit in need!!!
It may take some time 'til she gets used to live indoors and use the litterbox...during summertime Nellie refuses to use the litterbox, too (she's allowed outside during daytime), but now that she's older she prefers to use a comfortable litterbox rather than an soaked wet garden spot...just give Sally some time and she'll adjust...for now she has to learn that she has been really successful in finding a new home and that she's a keeper!!!

How lovely of you to take her in!!!