LR I don't know anything about this particular condition but I remember a friend of mine who's 6 month old baby developed an abcess on his eye and they feared it would blind him but he has made a remarkable recovery and his sight is near perfect. Children have amazing powers of healing and of coping because they believe what they hear. I would recommend your niece's family get another opinion if they can and above all stay as positive as they can with her. I will keep her in my prayers and hope that everything will turn out ok for her.
'I must be leaving soon... its your world now'
Glenn Frey 1948-2016 RIP