Ex starts in my school next year, what should I expect/do?

Was with her before TRP, me 16 y/o her 15, very great relationship. We took each other's virginities, lots of sex, lots of love. I broke up because I lost interest & wanted to focus school. I got back with her even though she was with a beta boyfriend. She started ignoring me because she didn't want to cheat on her bf. I started being very beta until I nexted her completely to avoid being more beta.

She's starting in my school next year and it's been 8 months since we last spoke. She has a beta bf atm. I usually walk a lot around my school and will most likely bump into her. What should I do once I bump into her? She will most likely be with her 2 very close friends because they will also start here, and I want to present a good image.

Let me know your advice, thank you!