Pregnant women only start getting symptoms after the fertilized egg and implanted, and thus is producing hCG. On the plus side, if she is pregnant and having symptoms that means she can take a test to make sure...on the down side, all of those symptoms are also common to monthly period symptoms.
Remember that stress can also cause those symptoms so if she does test before her projected period date (and it's negative) test again when the period is late just to be sure.