my godparents have outside dogs,but they have access to the garage all day and have a heater i nthe garage(thats where the cats sleep at night) but they sleep in the garage at night.They both have very thick coats,ones s husky/malamute,and the other is a Chow mix.they both love being outside all the time,but often come in at dinner time or whatever.

im glad that your SIL is trying to help the little girl