Gadsie, one thing to keep in mind as a young man at 14 you are still growing and probably haven't hit your final growth spurt. However, it is very possible the young lady the father has asked about has finished growing depending on a couple of personal things in her development. Therefore, 1800 calories may or may not be enough. Of course, as the others have mentioned she should eat her whole foods as needed/wanted and just stay away from the processed junk.
Just jumpin' in... I'm a 39 year old woman who didn't grow (except get fatter off junk food) after age 12.