I would recommend bringing 2 pairs of shoes - one supercomfy for days when you will really pile on the miles, and a second pair, maybe a bit dressier but still comfortable, for wearing to dinner or for days when you won't be walking as much. For example, we did an RS Germany-Austria-Switz tour a few years ago, and I took a pair of SAS oxfords [very comfortable but even my 80-year-old mother thinks they look too orthopedic] and Ecco sandals. It's good to switch your footwear from time to time so it can dry out and your feet can get a rest. In cooler weather, I've taken Merrell Mary Janes for my "dressy" shoes; I can wear them with socks during the day or with tights at night to look a bit nicer.
Probably the most important is to be SURE they are comfortable before you leave; she should wear them around home, to work, for several days in a row to approximate the kind of demand you will face on the trip.
Six weeks - what a great trip! Have a wonderful time!