What is Friendship???

My roommate and I were talking about friendship and how you learn who your real friends are. People you will learn eventually in life use you. Then when your not needed anymore what they really feel about you comes out and you find out that all along they just used you for a ride or for money. Unfortunately my roommate found this out today about her friends back home. What I then told her is what I'm sure everyone has said before, your true friends walk in when the rest of the world walks out. A code that every girl should follow is that you NEVER choose your best friends ex over her. That is probably one of the lowest things a "friend" could do.