1. Cause they can! Most women don't call other women on their bitchiness. Because women know this fact they instead bitch to all their friends about the other person in a passive aggressive manner. This just makes their bitterness towards one another escalate.

2. Because of a Man! Women, even the most secure woman, can get easily jealous if another woman pays too much attention to her Man. Even if that woman has no untoward feelings toward that man, just by paying attention to him you could be blasted either directly or indirectly (as is most cases) by that insecure lady.

3. She is wearing an outfit that you don't think is appropriate for her age or size. This is one of the most common situations I encounter. I, myself, have been known to critique the oddly dressed female or the skanky looking woman in too tight or too youthful clothing. I'll admit it. Most of the time women won't go up to one of these "offenders of style" and tell them constructively that they might want to tuck in their muffin top or that their camel toe is showing during the kid's soccer game. Instead, we make sure our other lady friends see what we see and then talk about it.

4. Misunderstandings. Women too often will rip their best friends apart to other friends because of simple misunderstandings. Perhaps it breeds from insecurity and feelings being hurt. Women are complex creatures.

5. Cause she deserves it. Every so often I find a woman who honestly is such a bitch that she really does deserve whatever smack comes her way. Some women are so mean and spiteful (for whatever reason - founded or unfounded) that they can't keep other women as friends. Maybe it's a mixture of the other 4 reasons listed here or perhaps she's just a bitch - Plain and simple. You can't help talking about a bitchy woman like this. These women are usually psycho so other women are forced to talk behind her back instead of confronting them head on...you DON'T want to get into a fight with a woman like this - she is the type to get physical and pull out your extensions, etc.