Medically, the issues are how soon did the ambulance get there, how soon was she stabilized, how soon was she intubated, was that process completed at the accident site or at the hospital, how soon did she get to a trauma centre, was there any brain injury, what was the glaucoma scale reading at the accident site, what was the reading at the hospital, how much time in a coma, what did the MRI show, etc.
Information is the only thing that will tell you what you are facing with your cousin and despite the good wishes and optimism of everyone here, that necessary information is the only thing that will really help you to realize the nature and extent of your cousin's current condition.
You will also have to gain some understand of injuries, medicine and surgery in order to put any information you learn into some sort of perspective, but you have the advantage of being much younger than I was two years ago, when I had to go through the experience and learning.
skieur