Why can't women have functioning productive relationships with each other? Are we our own worst enemy?

For years now I have tried to figure out why it is that we women feel the need to constantly compete with one another rather then form functional relationships and help each other become better people. I have a couple of close girlfriends and have made several attempts to introduce more to the our circle only to fail. Something always happens to cause some sort of falling out with someone. I have met women who feel better about themselves when you aren't doing well and are unable to be happy for you if things in your life are going well. This puzzles me as I thought relationships were to support and love each other and just plain be there. Am I mistaken?

I often hear women complain about the same thing, it seems to be a common problem and yet we can't seem to fix it. I work in an environment where I am in close quarters with many women and very few men, I am finding that this is true with women of all ages but had hoped that I would be able to bond with someone at the office.

Don't we have enough pressure without worrying about what your friends are saying or doing when you're not looking?