I think a girl can do whatever she wants, but sex can lead to pregnancy. Even if it is protected, accidents do happen. A girl that is still in elementary school should not be going through that at such a young age. A bunch of girls have had babies at that age, but really, what's the rush?
I think that it is not the answer to anyone's problems. It is just simply ending the problem without wanting to solve it. Certainly everyone has difficulties but that's what life is all about, overcoming them. And when you can straighten out your problems, you can appreciate life more and you'll be able to enjoy it.
On the other hand suicide is not completely a selfish act. sure, you are leaving loved ones and people in your life, but it is a personal decision whether to end your life and to be in a "better place".
You won't know what life has to offer, but if you end yours shorter than it has to be, you'll never find out.