What's it like to meet someone in your adult life who once made you feel terrible in school, and did it change the way you see yourself or them?

How do you deal with people who make you question your sanity when it was alright before you made communication with them? I would love to be their best friend, but it just doesn't work.
Should I be looking for (or is there) a meaning in my dream? I dreamt of going to a school reunion and knew everyone I saw besides one girl that I interacted more than with most.