“One good reason to only maintain a small circle of friends is that three out of four murders are committed by people who know the victim.”

Source: The Curious Incident Of The Dog In The Night Time

Source: Runaway

2019

"Outside Of A Small Circle Of Friends" http://web.cecs.pdx.edu/~trent/ochs/lyrics/small-circle-of-friends.html
Pleasures of the Harbor (1967)
Context: Look outside the window, there's a woman being grabbed
They've dragged her to the bushes and now she's being stabbed
Maybe we should call the cops and try to stop the pain
But Monopoly is so much fun, I'd hate to blow the game
And I'm sure it wouldn't interest anybody
Outside of a small circle of friends.

Many sources attribute this quote to Brown without giving a specific reference to her writings. The earliest located is the following variation from p. 47 of Musgrave Landing: Musings on the Writing Life by Susan Musgrave (1994), which Musgrave quotes as "Rita Mae Brown's warning": "If you become the kind of writer who calls forth heated emotional states, be careful. There are a lot of unbalanced people out there. The statistics on insanity are that one out of every four people is suffering from some form of mental illness. Think of your three best friends. If they're okay, then it's got to be you."
Disputed

Source: The History of Love

The Gun Seller (1996)

Source: It (1986), Ch. 16 : Eddie's Bad Break, §8
Context: Maybe, he thought, there aren't any such things as good friends or bad friends — maybe there are just friends, people who stand by you when you're hurt and who help you feel not so lonely. Maybe they're always worth being scared for, and hoping for, and living for. Maybe worth dying for, too, if that's what has to be. No good friends. No bad friends. Only people you want, need to be with; people who build their houses in your heart.