They say that a person in a coma can hear and understand you and that people whom they love and that love them should be there and talk to them as much as they can. They even say that being there is better than not as they can sense the presence.
Saying something such as ,"she'd be better of to die" is unthinkable to me as it is rude and uncalled for, and I imagine that would not help the person in a coma's spirits any. Things like that shouldn't be said at all and definately not in her presence. She needs motivation, inspiration and love to get through this.