Based on the pictures you've provided, it looks like there is some shed still left on the head and especially on nape of this snake as can be easily seen in the second picture. Is it possible that there is a leftover shed still stuck on her face? If so, stuck sheds do have a tendency to shrink as they dry and this can be pulling on her face causing this to happen.
If this is indeed the case, use a cloth soaked with tepid temperature water and use as a compress over the head for as long as you can and as often until the dead skin becomes soft and can be removed easily and without pulling on the scales underneath. Make sure you pull from the neck towards the nose as this always seems to be the path of least resistance and make sure if it's still on there as well, that you get the rostrum "nose" scale too.
Case in point: I had a hatchling that was unable to shed off an entire skin one time which caused her entire body to be very stiff and constrictive, even to the point of pulling on the scales around her mouth giving the impression she was "smiling". I used a light amount of petroleum jelly to help keep the skin moistened several times a week and basically had to wait until her next shed cycle which ended up, with a lot of help on my part, coming off entirely and she's now a very energetic and healthy wiggle worm. 
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Troy Rexroth
Rextiles
