losing friends is in my experience a somewhat dynamic and historically plausible process while break ups turn a switch in a woman's brain. i know this won't fare well with many folks to put it that way - but men don't have that switch. a woman turns from one minute to the other into someone else the moment the relationship is over and the only thing you have left to hope for is that this someone isn't going to be your new archenemy - especially if you have a divorce looking forward to.
I had quite the opposite experience. We're still friends since we ended our 6 year relationship. She is still the person I trust the most, and no one knows me as well. It requires a lot of honest communication. If one betrays the other, obviously that doesn't help.
Relaitonships are complex and diverse and there are many counter examples to what you describe.
