It's not about cosmetics that can be tackled with a high quality mask - it's also about all the practical functions that the face needs to tackle; e.g. the lip musculature necessary for speech and eating, eyelid/tearduct function, and nose breathing. If you're missing lots of tissue from your face, you will need a transplant (inevitably high maintenance) of some kind, so it might as well be a full-face one.

Besides the functional issues she has pre-transplant, there is the devastating daily effects of being seen as and treated like a monster by society at large. It would be bad enough to handle your own reflection in the mirror each day, but to know that everywhere you go you'd be treated as less-than, would be treated cruelly with some regularity, would be basically treated as sub-human by most people -- that kind of toll on ones psyche is immense, and there is little chance she'd ever have much quality of life.

If the choice is between being a monster guaranteed to be mistreated and abhorred by most people vs potentially being a somewhat decently normal-looking person, then I think there is no way that someone would choose the way of the monster.