heavy and runny discharge, white-yellowish color, little smell to it; before and after period

i have a friend under the age of 18. she is active and had unprotected sex. she says that it doesnt hurt or itch. it has a little smell to it. it bothers her a lot because she can feel it runny down. it leaves marks on her underwear. she doesnt want to tell her parants about it. what could this be?