When I was a little girl, it wasn't a Sindy doll or a My Little Pony I longed for, but a best friend. The kind of friend I could stay up all night with, whispering and giggling, confessing all my deepest secrets without fear of ridicule. A textbook 'lonely only', mercilessly teased by my schoolmates for my hippy parents and jumble school get ups, I longed to find a companion who would be more like a sister, the bond running as deep as blood.

What I didn't know back then was how dangerous a pact it can prove to be. When a love affair goes wrong we know what the rules are; we split our possessions, our friends seamlessly part like the Red Sea, lining up in the appropriate team, and we start the painful but predictable process of healing our broken heart and moving on to the next.

But when female friendships implode, there's no rule book to follow. It's open warfare: all you can do is run for cover.

My best friendship at university was just such a thing. Fierce and intense for those three years, it went disastrously wrong in our mid twenties. An argument escalated and turned spiteful and cruel, until I found that other friends I thought I'd had for life had been turned against me. If it had been a love affair I could have fought back, put my side of the story, but my protests sounded petty and mean spirited in this context. Now she's no more than 'Somebody I Used to Know', who I've watched marry and become a mother via grainy photographs on other people's Facebook newsfeeds. For years, a cocktail of pain and confusion would still rise up and choke me when I spotted that familiar lipstick-coated grin.

Why do we women turn on each other? We've all had those friends we meet for lunch, then walk away feeling way worse than we did before the starter arrived. They'll slyly undermine and belittle us, all delivered via subtle pinches that leave no visible bruises and can't be called out. Marriage and motherhood have been shown to be one of the prime battlegrounds between women. Is it our own secret fears around how we match up that makes us turn on each other, the problem safely pushed 'out there?'

Another common friendship killer is the 'foul weather friend' - the right hand woman who loves to comfort and support us when we're down, but can't bear it when we suddenly attain the (career, relationship status, weight - fill in the blanks) that we've always longed for. Many celebrity BFF break ups can be attributed to this phenomenon. Frequently fragile and narcissistic, our famous sisters are particularly prone to the kind of paranoia that can turn acid.

Paris Hilton is especially notorious for dropping her friends when she perceives their star is too far in the ascendant. Nicole Richie was the first victim of her froideur, cast out when she emerged from years of insecurity and neurosis and bagged herself a husband. Kim Kardashian was next on the Hilton hit list. As her reality series took off, and she became known in her own right, no longer billed as 'close friend of Paris Hilton', she reportedly suffered scathing public attacks from her one time bestie.

How can we protect ourselves from the pitfalls? Checking out is not an option: a life without girlfriends is a life deprived of a bond we cannot find anywhere else. Research bears this out: for both sexes, the biggest insulation against loneliness has been proven to come from strong emotional connections with women.

My new book, The Last Time I Saw You, is all about how we recover from the disastrous fallout of a toxic friendship. When her one time best friend dies in a car crash, Livvy is forced to go back and do battle with the ghost of their twisted relationship, uncovering a nest of secrets in the process.

For me, I know the friendships I've found in my 30s are of a depth and quality I couldn't have dreamt of back then. They might not have the same fireworks, but they have a solidity that more than makes up for it. There's no doubt that the fact I've left my own neurosis and insecurity behind is the deciding factor. Let's stand up for the sisterhood - there can be no doubt that we need each other more than ever.

Follow Eleanor Moran on Twitter: www.twitter.com/eleanorkmoran