I believe that it is completely normal. Sometimes, I'm late for a whole week and I'm a virgin (lol). If you are sexually active, or the period is late for more than two weeks, please see a doctor before symptoms worsens.
There are several reasons that a woman can miss her cycle. If you are sexually active you should take an at home pregnancy test to rule out pregnancy. If you don't get it i would see a doctor to see if you may have something simple causing the issue.