Looks like an abscess, but being so close to vital structures, I would just euthanize her. The recovery would probably be quite long, and the wound, after it got cleaned up, would be pretty cavernous. A friend of mine has had a few like that, and most of the rat's face on that side just necrosed out. He was put to sleep.

it would be in the rat's best interest to put her to sleep humanely.