My brother has 2 rescue cats that were abandoned by the mom. The one that bites is about 1 year old and really lovable, patient, doesn't mind being taken in your arms, doesn't run away when a stranger tries to take her, basically she's really relaxed. She's not afraid of large dogs and often follows them, curious. She also often goes into neighbors' house all along the street and stays by the fridge, hoping they will give them food (even if she still has snacks in her bowl here).
Now hopefully this will give everyone an idea of her kind of personality to explain the following. Sometimes my gf goes to the bathroom at night and the cat comes in at the same time and licks my face while I sleep, waking me up. Other times she walks on our face and explores around then slowly gets close to ears, nose, chin, fingers and bites for no reason when we're not even touching her. Not hard enough to hurt, just an annoying pinch.
I've read about cats biting on internet, how it can be because they're annoyed when they're tired of you petting them or want to assert dominance, however everyone seems to say it depends on the cat. From the info I gave, does anyone have experience with cats and has an idea what is wrong with her?
UPDATE: she does this all the time, day and night