09/15/2014 11:28 am ET Updated Nov 15, 2014

Is It Harder to Break Up With a Friend or a Lover?

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"I grieved it hard. I talked to only a few close friends, in spite of being a real talker, because I felt such shame about it."

"I was broken. This was my best friend from the fifth grade up into young adulthood. I don't know if I ever have truly moved on. I still miss her."

"I felt like I'd lost a part of myself. I had a hollow feeling inside all the time. I'd pick up the phone to call her (we used to chat for hours a day) and remember I couldn't call her, and I'd cry."

"I went into a deep depression that lasted for four years, during which I couldn't make any other friends."

These quotes are from a few of the dozens of women that took the time to respond to our survey at The HerStories Project about friendship loss, others who wrote to us, or those that we spoke to in person or online when researching our book, My Other Ex: Women's True Stories of Leaving and Losing Friends. Women who still carried around the hurt of failed or lost friendships.

While the details of the individual stories vary -- dissolutions due to betrayals and boyfriends, others falling apart under the stress of competition and envy, and many more friendships fading away with age and life transitions -- the feelings that women shared with us about their breakups were surprisingly similar.

During the first days and weeks following the loss of a friendship, when the fact of it is so raw and sharp, we've learned from women that it's typical to feel most alone, to feel embarrassed, depressed, shocked and obsessed with why and how it happened.

Sometimes that pain never truly goes away. It's a dull ache that can return when a familiar song is heard, a movie line is repeated, a Facebook status appears or an old picture falls out of an album.

We began our book project looking for answers. We wanted to know why these stories resonated so deeply with women, years and decades later, revealing wounds deeper than the scars left from romantic relationships. We wanted to know why women's friendships begin and end so differently than men's. We wanted to know why women seemed to feel more guilt, more shame, more trauma, and more remorse about the ends of friendships than the loss of romantic partners.

I wish I could report that we found definitive answers to these questions. But there are no startling conclusions. We can describe patterns and speculation, but in many ways we still feel just as confused and in awe of the power of friendship to support and comfort, as well as hurt and destroy, as we did when we started the project.

As experts in the field of friendship have described, there is a dark side to female friendship. Yes, there is unparalleled closeness, connection, support, and love, but there are also millions of women who carry around deep scars from painful relationships.

Destructive patterns and hurt can start very early in a girl's life. They begin on the playgrounds and in elementary school classrooms. Even today, young girls are still socialized -- and rewarded by parents, teachers and other adults -- as "good girls." While boys stereotypically handle conflict with physical and verbal aggression or more direct forms of confrontation, girls know that nice girls should never appear outwardly mean. They quickly learn that the socially acceptable way to channel their anger and feelings is to take them underground. They become masters at the subtle arts of exclusion, gossip, withholding friendship strategically, and other forms of manipulation to get their way with uncooperative peers and friends.

Girls become adept at what researchers call indirect or relational aggression. Rachel Simmons' research in the bestselling book Odd Girl Out: The Hidden Culture of Aggression in Girls, as well as Cheryl Dellasega's study of adult women in Mean Girls Grown Up, demonstrate that these strategies of using subtle emotional devastation to manage conflict can last a lifetime. Females learn to use relationships themselves as weapons--rather than fists, direct demands, and screaming. Their tools are the ability to undermine, manipulate, betray, and ignore. The devastation wrought can appear unintentional and difficult to describe or identify, sometimes masked by the careful image of the polite good girl.

There is so much good, so much power, so much love, in female friendships. But there is also a another side of pain and loss. And surrounding that dark side, there is often silence. Women feel that there is no language to talk about their feelings. There is shame, the haunting feeling that the loss of a friendship is a reflection of our own worth or capacity to be loved.

Our book, we hope, is a step toward breaking that silence. We as women need to recognize the scars of lost friendships and make it okay to talk about them. And we must also teach our daughters how to manage conflict and emotion without resorting to these forms of indirect aggression that cause deep pain with no visible wounds.

My Other Ex: Women's True Stories of Leaving and Losing Friends was published September 15, 2014. Visit the HerStories Project for information about a call for submissions for its next anthology, Mothering Through the Darkness: Stories of Postpartum Struggle.