Tell your friend, if her GPA is very competitive and MCAT's as well, then why in gods name does she care what anyone says? Exactly, if she does have a nice GPA, stellar MCATs, good EC, then she shouldn't be phased by anyone's dumb opinion, even if god himself told her she needed to stay in nursing since there was a shortage and that her chances to get into med school were low.
people care too much what others think, stop caring, just do what you want to do. If you have the necessary attributes to get into med school, then be confident that you can get in. How are you going to be a doctor with low confidence. "Hey this guy has cancer." think to self "should I give him chemo cause I know it is the right thing and something him and his family would want, or should I do what the other doctor said, 'don't give any hint of hope'" Do you what you learn, do what you should, and take others advice, comments, advice as a grain of mutha freakin salt.
Tell her if she is indeed disturbed by this doctors comment, then either her GPA/MCAT is not high enough, or that she should quit her dreams due to the fact that she is being affected by such an insignificant discussion. Make note of this last comment, no one, I mean no one who is seriously set on becoming a doctor should have to think twice about their desire after a pretty informal and quite insignificant discussion as that which you just described.