I stayed in a wonderful small hotel called Penon del Lago a couple of years ago, on the road between Bariloche and Llao Llao, extremely friendly people, really select, first class accomodation. I think I paid around 150 US dollars a night for a huge suite. Within easy walking distance is a great restaurant called Rincon Patagonico, highly recommended, particularly the lamb asado, possibly the best meal we had in the South, a great wine cellar too. I hope your mother enjoys her time in the area it is truly beautiful, I would suggest the best accomodation is away from Bariloche itself, it is just beginning to get a tiny bit tourist tacky.