Why do women unite around gossip and talking bad about others?

I know men sometimes do this some also but usually it is women and what is the psychology behind women doing this. My Dad was describing it to me when I mentioned some lies my mother was telling a few years ago and then asked about some gossip I heard from my step-mother about my mother and a friend of hers. He noted women unite around "I trust you enough I will bring you close enough to me to share these bad secrets about others I have" and then often the secrets are embellished or even made up. My step-mother does not lie but she does share things that don't need to be shared. My mother will lie based on "my emotion tells me this is true" where its a lie that she thinks could possibly be true.

So what is the psychology behind this and why do women unite around "I trust you so hear the dirt I have on others".