'I helped my best friend cover up her affair. Then she betrayed me in the worst way possible.'

It was a year seven peer support group that introduced me to *Fiona. She was loud, confident and hilarious. I was more reserved and deep in the overwhelm of starting high school. Fiona took me under her wing, slowly bringing me out of my shell.

We fast became a double act. Me, the not-quite-cool, studious rule follower and Fiona, the cheeky, very cool, rule bender seemed like an odd match, but we worked. I became a regular at her house where the vibe was not quite as strict and buttoned-up as it was at mine. I adored her family and loved how they welcomed me as another daughter.

Fiona had her pick of the boys. If her personality wasn't enough, she developed way before the rest of us, growing a pair of boobs that were the talk of the town. Boyfriend after boyfriend came along. Fiona devoured them and spat them out, leaving a trail of heartbreak behind her.

Bored of school, Fiona left after year 10 while I carried on and went to university. Our friendship stayed strong and we ended up in a share house together in the city. Our social circle was big, mainly people that Fiona brought into the fold, including a sweet girl named *Bettina.

The three of us played in a mixed Oztag team on Friday nights alongside Bettina's boyfriend, *Marcus and a few of his friends. It was more social than sporty and pretty much just something to do before we hit the local pub.

Fiona was an Olympic level flirt. Her skills had served us well over the years as we benefited with VIP access, free drinks and hotel upgrades while she smiled, complimented and winked with abandon. She flirted with everyone, including Marcus.

Knowing that flirting was Fiona's natural state, Bettina didn't seem to mind. We'd lost a few friends over the years who had quickly veered away from us in order to protect their men from Fiona's charms, but Bettina was different. I soon felt sorry for her, sweet trusting ways.

It might not have been obvious to everyone, but I could tell that this Marcus thing was growing to be more than casual flirting. While Bettina and I waded through the muddy carpark at the Oztag fields, Marcus ran past us with Fiona on his back, protecting her new shoes. When Fiona needed to pop down the road to the ATM, Marcus went with her "because it was late and dark out there".

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I warned Fiona to be careful, that it looked like he was falling for her and a lot of people could end up hurt, but she brushed off my concerns, assuring me that nothing was happening.

Finding Marcus rifling through our fridge in the early hours one Sunday morning wasn't as shocking as it should have been. I knew this was going to happen.

Fiona promised me that it was a one off and begged me not to tell Bettina. It didn't sit well with me, but I loved Fiona and would have done anything she asked.

It wasn't a one-off. Fiona and Marcus continued to sleep together for years. Even after he and Bettina got engaged, long after our Oztag days were over, the two of them would catch up every now and then. It wasn't love, it was a pure physical attraction that they were both addicted to.

Fiona continued to date, eventually moving in with a lover, keeping Marcus in the wings.

Bettina and Marcus got married and started a family. I was there through it all, alongside Fiona, with my mouth firmly shut and the guilt eating away at me.

As I entered my own first serious relationship I realised that harbouring that shitty secret had created my own trauma and trust issues, particularly when it came to Fiona being around my lover. For the first time ever in our friendship I was stern with her. "Don't you dare start with him, I mean it. I won't tolerate you disrespecting me or my relationship."

She behaved herself, but my chaotic distrust was the end of that union. It was too much for him, a good guy who didn't deserve it, and he split.

I started counselling, working through my issues, a surprising amount of which had roots in my friendship with Fiona. When I was offered work in another state, my therapist thought it might be a good idea to get a little physical distance between us for a while to help me rest and evaluate.

It was a great decision. I moved, my career flourished, I fell in love. My family eventually relocated too, life was good.

Fiona was a regular visitor, obviously, but still cautious, I would hire hotel rooms for us to stay in rather than invite her into my home to be around my now fiancé, *Dean. It was under the guise of 'girly weekends' and she didn't seem to mind. In fact she enjoyed it so much that she ended up moving to my new hood too.

It was fine. Fiona had matured, she was respectful of my relationship and I learned that she had finally ended things with Marcus. She'd had a wake-up call about her behaviours after losing a job she loved when she slept with two of her bosses. Naughty Fiona was Good Fiona these days.

Still, Dean wasn't very fond of her. He found her tedious and was slightly resentful about how much of my time she took up. I'm ashamed to say that I liked that he didn't like her.

When Bettina and Marcus brought their brood to town, I was thrilled to see that Fiona had not been lying. We all spent time together and it was clear that the electricity that I'd always known between her and our friend's husband was no longer firing. He seemed like a dedicated husband and father.

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But when Bettina pulled me aside for "a chat" the energy was all wrong and all of a sudden I had a feeling that she knew, and she was about to ask me what I knew. My anxiety spiked as I prepared myself for a conversation that was a decade overdue.

"*Alicia," she began. "I don't know how to say this, but I just saw Dean and Fiona kissing by the ATM."

I have no memory of the next hour or so. Apparently I just froze, not able to speak as Bettina steered me out of the venue and back to my home where she called my mum and sister to come immediately.

An overwhelming guilt about what a terrible person I was to Bettina was all consuming. It was like my brain couldn't process the news that she gave me, but rather focussed on the fact that she immediately told me what she had seen, while I had kept much worse from her for much longer.

I recall hearing Fiona and Dean at the door shouting and begging to be let in, not able to get past the bulldog security team that my family had formed while Bettina nursed me through a bout of hyperventilating. Weirdly, I still couldn't begin to process the betrayal that happened to me, but continued to focus on the way that I had betrayed Bettina who stayed with me through the night as I sobbed in my bed.

Eventually it came to light that the reason that Fiona was able to end things with Marcus was because that Dean had taken his spot. The two of them had been sleeping together ever since she moved to town.

My heartache was immense. I became a shell of a person. Mourning my relationship was one thing, but mourning the friendship with Fiona was like a death. Rage and sorrow overtook me in turns.

Bettina held no anger towards me for not revealing the affair before. She even forgave Marcus. She is a better person than I'll ever be.

But we're both better people than Fiona.

Feature Image: Getty.