Her face changed so much because her mastication muscles basically shrunk due to her weightloss and low-cal regime. If you go back and look at most models who have lost a sizable amount of weight, you will notice all of their jaws are slimmer. Eg; Coco Rocha.
You can get something similar done with botox injections into jaw muscles, so as to immobilise them, which means they won't be used during eating and so the muscles waste due to disuse. Something similar happens when you break a leg or arm and it's put in a cast; after weeks the muscles become weak and shrink because they weren't being used. Google 'jaw muscle reduction with botox' for curiousity.
EDIT: I can't for the life of me fathom how wisdom teeth taken out can have any pronounced effect on your jaw. The angle of the mandible/jaw is a bone wrapped in a lot of muscle. Which is where we see the change in abbey's case.