As told to Ann DeGrey.

I got the birthday invitation from Petra* out of the blue. We hadn't spoken in more than 20 years, though I went to high school with her and had fond memories of her.

She was always the quiet girl in the back row of the class.

We were never real friends, just familiar faces.

Still, the message was warm: her 40th birthday lunch at a nice Italian place.

She said it was just a small group, and I'd know plenty of people there from school, so I thought, why not?

I RSVPed "yes" and bought her a pricey scented candle as a gift. So, I was really looking forward to it.

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The restaurant was nice and cosy and Petra was already at the long table by the window, waving me over and giving me a hug.

She introduced me to the other women, who were mostly people I half-recognised from school, plus a couple of her work friends. Everyone seemed relaxed, and we got stuck into the prosecco, chatting about our kids and how crazy it was that we were all in our forties.

For the first half hour it felt normal and really pleasant. But, after the main course, Petra stood up and smiled. First she thanked us all for coming, but then she looked straight at me.

"And I especially want to introduce my old classmate Helena* (me!), the person who bullied me in high school and got away with it."

The table went quiet and everyone looked quite shocked. I thought she was joking, as there was no way I was a bully.

I said something like, "What on earth are you talking about, Petra? I never bullied you. You must be thinking of someone else."

Then she told everyone that I used to wait for her in the hallway and make comments about her weight or her hair.

There was no way that was me! I did remember giggling with my friends when she turned up one day wearing a funny hairstyle, but I had no memory of doing anything else.

She said I'd mimic her quiet voice in front of the other girls, turning her into the butt of jokes.

Then she added things I couldn't even place; stories about me spreading rumours that she smelled bad after PE, or that her family was poor and that's why she never went on excursions.

There was no way that happened because I was the one that came from a relatively poor family, not Petra. She said I made her dread coming to school, and she used to cry in the bathroom because of me.

Her eyes stayed on mine the whole time, like she was sharing something brave. None of her stories matched what I remembered. Yes, I recalled teasing her sometimes. I might have said, "Nice hairdo again, Petra," in a light way when she walked by. But I was never mean or nasty.

I never waited for her and I certainly never mimicked her voice in front of others. And I have no memory of the rumours? I had no idea where those came from. I never talked about her family or her smell or anything like that.

But Petra made out that she was relentlessly bullied, and I was the perpetrator. It was simply not true! She then said she'd carried that hurt for decades and how therapy helped her finally name it as bullying.

"Inviting you today was part of my healing," she said, smiling. I was in tears by this stage, telling her several times, "That's not how I remember it." No one looked at me with anger, exactly; just awkward pity.

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The rest of the lunch dragged on while people tried to move on to safer topics like holidays and house prices. Petra smiled at me now and then, like we were even now. Had I really hurt her that much? Or had time turned light teasing into something darker in her mind? Maybe she needed a villain for her story. Maybe she had rewritten the past so she could stand up today and feel strong.

After lunch, I sat in the car. I sat for a long time, feeling pretty shell shocked. All those years later and high school could still reach out and slap you. I thought about texting Petra, explaining my side, but I knew it wouldn't matter. She'd already built her moment and I'd walked right into it.

All I could do was drive home, listen to some music and remind myself that the girl I used to be wasn't a monster, just a teasing, clueless teenager. And that sometimes old friends aren't really friends at all.

*Names have been changed to protect privacy.

Feature Image: Getty (Stock image for illustrative purposes)