Sorry if I'm posting at the wrong section, unsure where to post my question. But I am posting on behalf of a very close friend, she told me that whenever she is about to have her period, she will always need to go to the toilet and purge , somewhat like diarrhea, and it's almost everyday , few times a day. Is this a possible sign or symptoms for girls that their period is coming ? Or it's just purely coincidence ?

It's common. The hormone changes and causes more bowel movement and stomach discomfort. I prefer the diarrhea compared to the continual extreme stomach cramp.