I think you can be pretty and disabled. But it also matter on the disability??? I've seen pretty girls with missing limbs and once in a wheel chair. But if it was a mangled birth deformity, I would notice it too much. I don't think its just the face its the whole thing. The body, the hair, the posture, the make up, apparel and so on.
Attractiveness is subjective. There's people who think tattoos, overweight, scars, dyed hair and pricings automatically make someone undesirable. Then there's people with the opposite reaction. Cant make everyone happy.