By taking the morning after pill, this can throw off her cycle and in her case, which in her case, she started early. Her whole cycle may be changed, or she may still end up with her normal period in a week again. As this can cause cramping etc. since it wasn't her "own" body that has produced this period. If the pain becomes severe, or something that Motrin doesn't help with, then she should be checked just to make sure there is no type of infection etc. But keep in mind, since her cycle was lighter, she may be getting ready for her actual cycle, as this can increase stomach cramping, due to hormone changes.
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