Why are female bonds so strong? And why are we so upset when they break, some say even more than a romantic breakup? Generally speaking, you can leave two women who've never met in a busy doctor's waiting room and by the time they're called for their appointments, they know each other's life story and have traded phone numbers. Much of this behavior has to do with female brains and hormones.
The Female Brain
Most women, far more than men, mirror other people and their emotions exceptionally well. One reason is that women's brains have many more neuron cells (in both hemispheres) devoted to body sensations and emotional processing. A woman sitting with another person immediately begins to mirror that person, matching and simulating his or her breathing rhythm, muscle tension, and brain circuits. She is able to monitor infinitesimal changes in that person's expression, and search her emotional memory for cues and clues to what he's feeling.
So they're better at anticipating, judging, and integrating emotional reactions, both positive and negative. They read things like someone's pause in speech, the tightness of someone's mouth, or a low flat vocal tone as essential clues to another person's state of mind and needs. The same clues go right by most men. Women respond with anguish when faced with another person's pain to a much larger degree than men.
The chemical effects of hormones also enhance women's powers of perception in the realm of feelings. Women have more estrogen and a greater default level of the hormone oxytocin-the human chemical that makes two people want to bond at the mere touch of hands, or even the idea of touching someone. So, women feel more intense emotions and physical sensations of pain, pleasure, and everything in between.
Early human history also plays a part. These female traits are the vestiges of prehistoric woman's need to be nimble enough to discern friends from foes and get the children out of harm's way as fast as possible. If her safety was threatened, a prehistoric woman did not usually stand and fight, as a man of her time (and now) more likely would. She needed the support of other women (and men) to watch and protect their group from external dangers-animal, human, or otherwise.
Smell and More
In addition to women's greater ability to perceive and mirror emotions in others by using visual cues, females have a more a perceptive sense of smell than males. This goes back to estrogen, and since women have much more of this hormone, their ability to detect odors is more acute.