who did belly choose

Belly chooses Conrad at the end of "The Summer I Turned Pretty" series. After a complex love triangle with Conrad and Jeremiah, the finale shows Belly realizing that she has always loved Conrad. Despite her initial uncertainty and a temporary separation, she ultimately chooses Conrad, affirming her love for him and deciding to be with him in the end, symbolized by her catching the train to be with him after he departs for Brussels.