idk if you had decided where she went to school when she was younger but maybe ollie was friends with her older brother? they could have lost touch when ollie went away to school on the east coast (which can also be 100% ollie's fault, i have a feeling he went MIA on a lot of people) and it was awkward when they ran into each other again? he also had a well-off upbringing so they could have lived in the same neighborhood of prospect and/or her parents could be friends with his mom and stepdad?