October 29, 2002:
The dynamic plays like this.
Goes to her girlfriends seeking validation for her point of view. She's not seeking an objective pair of neutral eyes: she's seeking agreement, in the strongest possible terms. Paints a picture crafted to encourage a reasonable person to support her decisively. Is so expert at this that many times they'll experience real outrage that anyone could be so cruel, or heartless, or bad.
The first few times this happens, the girlfriends are shocked at how unreasonable her new boyfriend seems to be. Over time, repetition creates a strong image: this man is no good. She's picked another loser. The sooner she gets away from him the better.
Returns to her boyfriend armed with her girlfriends' reactions. "Girlfriend X says you're treating me badly. Girlfriend Y says you're a horrible person. Girlfriend Z says I'm too good for you."
The first few times this happens, he's shocked at how unreasonable her girlfriends seem to be. Over time, repetition creates strong images: Girlfriend X is vicious, Girlfriend Y is petty and mean-spirited, Girlfriend Z is either crazy or jealous. He feels persecuted and becomes angry.
Eventually the two camps come to open war. The relationship is torn apart by these buffeting currents. To be more exact, they contribute.
The process is blind to gender. The girlfriends come to dislike each other. They especially despise her sister, who detests them in return. The war simmers, but the outcomes require more time, and have certain constraints lacking in her male relationships. She can't dump her sister, for instance; and she's not as quick to walk away from her girlfriends. Still the same end is inevitable.
Eventually she mistrusts everyone. In her eyes they've mutually discredited one another. She has no insight into her responsibility. She feels she has to start over with new friends.