I totally agree. It makes us seem like we never truly leave adolesence, where we can never find the point where we look our sister's/best friend's/co-worker's/roomate's boyfriend/husband/recent ex-boyfriend/husband in the face and say, "You must be joking if you think I'd do that to her."

Its competitiveness at its highest degree. "He wants me MORE than he wants you." Apparently being wanted sexually is grounds for decimating bonded female relationships that usually mean much, much more.

Sad, sad, sad.

And I've done it when I was young with my friend. She dated literally everyone in the world and hated to lose an admirer. Sometimes she just briefly dated guys or sometimes it was something much more. She dated someone in briefly in high school that I then dated for five years starting in college, and I could never trust her alone with him. The minute I blinked she was in his personal space. Who was wrong? Me or her? I'll never figure it out.

And throughout our entire friendship, every time I confided a crush to her, she promptly went and slept with him. Sometimes she tried to keep it from me, sometimes not. So after more than a few years of this I started exacting my own revenge. It doesn't feel good now, but it did then. Unfortunately I think we've hurt each other equally, and its a shame we hurt each other at all.

She was (then) prettier and had much more self-esteem than I. I have come to think I wasn't so much a best friend as a booster for her, a wing-man of sorts. But oh, how things have changed.

And I have no problems leaving her alone with my husband. Ever.