In my opinion, she should eat only meat, fat (olive oil, bacon, butter, fatty cuts of meat) and vegetables for a while. She'll probably lose weight that way. Best of all she will lose the fear of missing a meal. The treadmill doesn't do anything at all except maybe keep her mobile. She needs to build muscle and bone. She needs to build enough muscle and bone that it offsets most of the weight she loses from fat. She can only do that under a load so she's going to need to lift some heavy things.
This is a very long video and you and I are not the audience, but I was floored by the information in it.
Jonathon Sullivan video
Roughly the same information from the same guy, in text instead of video
Female, 5'3", 50, Max squat: 202.5lbs. Max deadlift: 225 x 3.