I got a boob job two years ago. My best friend, seeing the results, wanted one, too. When she realized she couldn’t afford it, she started making snide comments about women who get them. Recently, a guy was hitting on me at a party, and she started flirting with him and asked, “Do you think I need a boob job?” and told him I’d gotten one. I was shocked. I’d like to say something to her, but she’s the louder part of my friend group, and I’m unsure how.

—Disturbed

Self-defense for men is karate or maybe Krav Maga. For women, it’s ducking mean remarks.

Many people have a romanticized view of women as the sweet, ever-nurturing “better angels of our nature.” That’s a major myth, but it continues to have traction due to the nature of female rivalry, which is much like slow-acting poison gas. (It’s often hard for a woman to recognize she’s been dosed…till she’s writhing on the floor like a goldfish sucking in its last desperate breaths.)

While from boyhood on, guys tend to relish competition and are openly aggressive (like when one socks another in the jaw), psychologist Anne Campbell describes female aggression as “indirect” and “covert” (sneaky and hidden). She believes women evolved to compete this way to avoid physical harm that might have damaged their ability to have or care for children.

Common sneaky ladywar tactics include weaponizing a group of women against a targeted woman by spreading nasty gossip about her and rallying the coven to ostracize her. In the presence of a man or men, one woman will try to undermine another woman’s mate value by revealing her supposed hussyhood or trashing her looks — as you experienced.

Men tend to prefer natural breasts (though their eyes go boi-oi-oing! at the big, pert fakeuns). Your “best friend,” spotting that a guy seemed into you, performed the vital public service of informing him your bodacious boobs are, in fact, siliconey islands.

Why would she do this? Well, unbeknownst to you, you violated an unspoken rule of female society by amping up your appeal to men via Boob Fairy, M.D.: openly competing with other women. It’s the “openly” part that’s the problem. Psychologist Joyce Benenson explains that, in contrast with “the constant male struggle to figure out who is better, faster, smarter, or otherwise more skilled,” girls and women enforce “equality” among themselves and resent and punish women who stand out.

“Should a girl appear superior, even accidentally,” she is guilty of a crime against the rest and “faces social exclusion.” This carries through to adulthood, with the thinking (summed up by Benenson): “Nice women don’t try to outdo their female peers.”

Of course, women do compete. But, Benenson notes — per interviews with hundreds of women by various researchers — women deny they compete with one another, even to themselves. This subconscious self-deception — “a woman’s honest belief that she never competes with other females” — allows her to do just that without any pangs of conscience getting in her way.

That’s one reason why confronting this woman about what she did might be problematic. Additionally, research by evolutionary psychologists Tania Reynolds and Jaime Palmer-Hague suggests your standing up for yourself — telling this woman her behavior was out of line — could be portrayed by her (to other women in your circle) as your victimizing her! Thus putting a big stain on your reputation!

Compared with “traditional forms of gossip” (the sort readily perceived as catty and mean), women’s disclosures of a friend’s hurting their feelings (kindness “violations”) get a pass, Reynolds and Palmer-Hague observe. They are “relatively trusted and approved,” suggesting women have “a social blind spot” to a tool used to trash the reputation of other women. Reynolds explained to me via email: Basically, if a female friend says about another woman, “‘You wouldn’t guess how mean Mary was to me the other day,’ you’re less likely to recognize this friend’s disclosure as gossip.”

In their research, disclosures like this “effectively tarnished … social opportunities” of the women they were made about. “Participants evaluated women who treated their friends poorly as immoral,” avoided having them as friends, and wanted to “warn others about their bad character.”

You might decide to say something anyway: gently tell this woman you prefer to keep news of your boob job unbroadcast. Note that even this approach could be turned into ammunition against you through a “victimhood” story she might tell.

Consider whether you have the social and emotional capital to bear the potential costs — while factoring in the psychological cost of just sucking it up and saying nothing. Ultimately, though many women are nothing but supportive of other women, it’s wise to remain mindful that, well, behind every beautiful woman is a crowd of other women looking to push her into a shed and padlock the door.