Barbara, when cats pee'n'poop outside they mainly use loose soil, sand and barksnippets (Rindenmulch)...so maybe they should try this as a litter substitute for available cat litter...as soon as Bodo Girl accepts the box with this familiar kind of litter her new family can gradually exchange this familiar litter with the pet shop cat litter...

During summer Nellie hardly never ever uses her litterbox, but as soon as it's getting uncomfortable outside she uses her box and I am sure Bodo as a clever girl will learn the comfort of a litterbox during wintertime pretty soon...

Hope this helps...