They had their first kiss at the end of *Harry Potter and the Half-Blood Prince*, and Ginny's feelings for Harry are implied throughout *Harry Potter and the Deathly Hallows*. While they don't have a huge romantic storyline during the book, their relationship is a source of comfort and strength for both of them.
It's important to remember that the main focus of *Harry Potter and the Deathly Hallows* is the battle against Voldemort and the consequences of the war. Their romantic relationship is a backdrop to the larger story.