How Soon Will A Person With Brain Edema Recover?

My sister was injured in road accident in Riyadh when their car collided head on with a stray camel on the highway with speed of car at 220mph. My nephew and she were brought to hospital "ventilated with tachypnea and spontaneously decerebrated as well in all 4 limbs" "CT scan showed global SAH with bleeding of cisterns at base" Brain edema was present. Now it is been 3 weeks (19th February at 1 pm midnight). still in ICU lying unconscious. Please tell me how soon can she recover?