Why, as women, do we tend to put each other down?

Tenasia
I was having this discussion with one of my friends and we noticed that a lot of times women put each other down rather than lifting each other up, but why? For instance, an old "friend" of mine was constantly trying to throw shade at me and out me down and I find that a lot of women tend to do this. Shouldn't we be supporting uplifting each other?