Agree with all the above. I took my lot to Shiga and Nozawa for their first Japow trip. Shiga for ski area, Noz for cultural feel etc.
80-90% of accomodation will have shared bathrooms. They are always spotlessly clean. A lot of western women struggle with the share factor. It is Japan, embrace it and it will embrace you.
Accoms in Noz, mid Jan can be difficult, but keep looking and you will find, especially 12 months out. Some places only cater/take bookings from large groups, and others dont open there books until a few months from the season opening. If you look hard enough, you will find direct email addresses for accomodation places, these are gold.
Tip; look for accoms around Nagasaka Gondola, it's kinder on the legs.