Why do we girls bleed?

Hi Rosella,  unfortunately you will not like what I have to say because as you know everyone grows up (you can't be a peter pan or a tinkerbell forever).  As you grow up you experience puberty and with puberty for girls comes a  period.  We have periods as we produce eggs and those eggs get released once a month to the ovary and since there is no sperm to impregnate the egg with, you shed your lining which is called a period.  There is nothing that you can do that can prevent you from reaching puberty, you could talk to your mom as there is some birth controls that take away your periods and that you would only have them a couple times a year but to be honest it is healthy getting your periods for awhile so that your young body knows what to do. 

Hope this helps and wish I could help further...