I, too, definitely think it's the same girl in all 4 pictures. Lips, nose, hair, everything. Look at the weird way she has her lips pursed in the photo with the white shirt without the headphones, then look at the cropped photo - you are viewing the same thing, but from a different angle. Probably something she did a lot. Or maybe she was camera shy. Just my opinion!
Also, if you look at the cropped photo where she is just waking up (we hope), you can see the part in her bangs is slightly off. It is the same part in the headphones picture. I think she ran a comb through her hair, maybe just her fingers, but did not change the part from the way she slept.
I think you guys have done a super impressive job sleuthing out these pictures. Keep up the good work. I've been looking for a missing person that resembles her, but nothing yet. I hope she is alive. Maybe that's why we can't find her.