How can I help my friend?

Every few weeks, my best friend has a major break down and verbally abuses everyone she loves. She spends a whole night sending me emails and instant messages telling me that she hates me, and various other things. The next night, she either calls crying to me about what she said the night before, or sends me an email. Here is one such email:
"I was built on a foundation of love, and grew up in a loving, and caring family with a mother who taught me to be affectionate. I was built up on all of this, and as I grew older, I became harder and more realistic. I began to understand things. I developed a shell. It became very easy for me to be outwardly affectionate, but inwardly very hateful and numb to most feelings. There was anger, frustration, sadness, and sometimes pleasure, but over the years I had to accept that I was, and am, a very selfish person. Most of what I do is for myself; I fish for compliments. I cling to my friends and acquaintances; I have an innate need for love, companionship, and simply put, attention.

Most of the time I find it very difficult for me to give a damn.

But if you're lucky, I do.

I am not grown up. I am fifteen years old, and a freshie in high school. The primary things on my mind? Sex, graduation, college, future career. I was not built on the foundation of traditional morals. I am not proud of who I am, or rather, who I have come to be; I will not flaunt the fact that a very sick little child within me gets some sort of sadistic pleasure out of knowing that I have the power to destroy someone, to **** with them to my heart's content. This is not my redeeming quality, and I have accepted the fact that this cannot change by simply me willing it away.

I need to be <edit>by fathom, reason: off topic</edit> with as well. Lord knows deep inside I wish I could be struck down a thousandfold with all the terrible things I've done to people, men and women alike, but I know that this is not possible.

There are certain things that happen in life that make you wish you could turn your life around; things happen that give you a little more insight, a little better understanding of the way clocks tick in the world around you. Situations such as these have simply been building up on me and I have been ignorant enough to let them slide by me, and I have pushed them away. For several years I have taught myself to live for the present, and live life as if I were to die tomorrow. FAILURE, again. The past haunts me; the future lays its cold, lifeless hands upon my throat and chokes away my present-day visions.

I have a life to live. I am full of vision and talent, and there is plenty that I can do to make the world a better place for not only myself, but for those around me. If I could only learn just a bit more, perhaps that will be incentive for me to give a damn more than what little cares I have.

I am petty, I am childish, and I am terrible.

I will not be the first to admit that.

But I, like every other animate and inanimate object on this planet, am subject to change. Maybe not by my own hands, but I leave it up to my closest acquaintances to lend a helping hand. I cannot grow up on my own. I am in tears; my childish soul wishes to break free and allow me to finally mature.

This is a cry for help."

She has never hurt anyone. The worst shes ever done was maybe...once in two months verbally abused me and her father. She suffers from severely low self esteem, depression, and lonliness even though she is surrounded by people who love her. I want to help her, but I dont know what I can say to not make things worse. She gets over it in like...two or three days, but even when everything is back to normal Im afraid for her. I dont want her to hurt herself. Her father is keeping a close watch, and I would most definitely trust him, but Im afraid that he cannot protect her from herself. email me at [email protected] if you can help me fight these bi-monthly depressions.