I think you missed my point. It has nothing to do with her capability. There is logistically no way for someone to walk or run on those roads in February. The same ice that caused the crash would have rendered her unable to run. Some of these roads are closed to driving this time of year due to the icy conditions. She had to have had special shoes - either hiking/studded boots or snow shoes (or ice skates) in order to get 20 miles on foot. It is not possible otherwise. Alternatively, she would have had to cross country ski if not hike.
Yes, it is possible to run/walk that distance with appropriate clothing/gear and that includes footwear. There's no indication Maura had that the gear. If she didn't, she would not make it 20 miles. You can't just put on regular walking shoes and expect to walk across ice standing upright or in 5 feet of snow, especially in the forest at night. She would have died long before she got to Loon if she tried such an endeavor.