Yikes! This is much heavier a topic than you usually see here. I also think it would be better suited to Other Chat but I've decided to end my fiendish mini-modding ways.
In short, no.
In long, noooooooooooooooooooooooooooooooooooooooooooo.
A nine-year old girl probably (and I say probably) isn't mature enough to go through the emotions that precede/proceed sexual activity. It really also depends who it is with. To tell you the truth, if it was with another nine-year old then fair enough... its the individual's choice. But if that person is older, which would be in the majority of cases, then it is taking advantage of innocence immaturity, which is very wrong indeed.