This article contains spoilers for The Summer I Turned PrettyAfter a long wait since we were blessed with season 2 of The Summer I Turned Pretty, we are finally making our way back to Cousins for a summer we will never forget. The Summer I Turned Prettys third season has begun filming, and us fans are exploding with anticipation for what could be in store for this shows conclusion. The popular Amazon Prime original show was based on a popular YA novel trilogy by Jenny Han.