Why do girls flirt when in fact they are just 15 years old?

Names for the people has been edited... I have a male friend who is 13 years old , he told him that in his class which everyone is also 13 years old , there is a girl named V and a boy named M who are dating , M's finiacial state is a little above average and he is always borrowing money from his classmates to buy gifts for V. One day , my friend let's call him X , X told me that V dumped M. And she went for another boy named R , she kept SMSing R to tell him sweet things and stuffs like that but R didn't fell for her treat and rejected her.So a few days later V went back to M and not long after V contracted chicken pox , a few weeks later my friend K told me that when V returned to school she was scolded by everyone A Prositute I asked my friend why they scold V a prositute and he told me that when V was not feeling well when she contracted chicken pox , M took care of her and even slept with her! Can u believe this , they are all only 13 years old!!!!!!!