Adult narrators who reflect back may fall into the trap of filtering their teen experiences through their adult sensibilities. That is, now that they’re wiser, they’ll comment on why they or others chose to do what they did. That’s more likely an adult book than YA. Teen protagonists aren’t that mature yet, so if you write your ladies as young people, they’ll be more likely to just judge, act, and react, without considering their or other characters’ true motivations first. They’ll mature by the end of their adventures, but they won’t start out that way. You can save their eventual meet-up for an epilogue.