Woman-on-woman crime happens when another woman sees your pantry and says, "Oh, you're not buying organic?"
It happens when you say behind another woman's back, "I would never treat my husband like that."
In short, it happens every time you judge another woman for making a decision you wouldn't make.
Woman-on-woman crime has a huge, ugly mole on her face called "Mommy Wars," which, again, you have probably observed, if not experienced. You can identify a mommy war when you hear things like, "haven't you heard that breast is best?" or, "Oh, I would never let my child cry it out."
Mommy wars, wife wars, food wars, fashion wars, friend wars. They're all woman-on-woman crime.