Where does forgive and forget end?

I’m not sure where to post this.

Basically, an old acquaintance of mine reached out today and told me they’re sorry for what they did two years ago and would like to try and rebuild a relationship.

Two years ago was junior year of high school, where they spread nasty rumors about me and created a really difficult social situation. I lost friends because of them and was ostracized because of rumors I couldn’t prove untrue. A lot of tears were shed and a lot of emotional damage was done.

I told them I appreciated that they reached out and thanked them for the apology/explanation (basically super insecure and projected onto me). They’re dating somebody in my close friend group, so they’ve gotten invited into our group chats and stuff and I have to be around them electronically fairly often. How far does forgive and forget extend? I want to, but I healed from that part of my life by forgetting about it and sealing it over and now that they brought it up again all of those feelings are starting to wash over me again and I feel super insecure around them. I don’t know what to do.