At primary school/secondary school I had a friend. Well, I say friend, but in reality she was a mean and hurtful girl. I know she was a child, but things people do to us as children really stick.
She would go from being my best friend to completely ignoring me in favour of the 'popular' girls, and did things that really hurt me. She told the class I (and my sisters) had headlice, which meant I had no friends for about 6 months as no one wanted to go near me. She made friends with people who were bullies and didn't like me, so she would run away from me in the playground, or say we should play 'hide and seek' where I hide and she would never come. Things like that. But months later she would come back and like a foolish child I would accept her back, mainly because I was so lonely and had no other friends.
At about 14 we completely went our separate ways and I never looked back. In my mind, she was a little cow and I didn't need her toxic nature in my life.
I tried to separate myself from the person I was back then and don't associate with anyone from those days, I moved away when I went to uni and even now avoid going back to my hometown more than three times a year or so. It wasn't just this girl, I suffered bullying and had many awful experiences during my school years.
Fast forward a few years and I am in my mid-to late 20s. My sister who is six years younger than me now works at the same place as this girl and they've become good friends. As in, more than colleagues, they're on each other's social media and speak outside work etc. She (my sister) says this girl is really nice now. I know I'm probably being irrational as it was over a decade ago and she was a child, but I can't help but feel a little uncomfortable with it. I understand the need to be civil with colleagues, but they've become very pally. My sister says I should forget the past and have a 'reunion' but there's no way I could do that. I know she was a child, but she knew she was hurting me.