Underage at the time of the Final Battle, she hadn't been an active fighter. Sure, she snuck out of the Room of Requirement the first chance she could to get in on the action, but not as much as she had hoped. It must have been frustrating to see her entire family in danger, including the wizard she was in love with, and be unable to do anything. Her older brothers had been incensed when they discovered her outside of the protection of the room. Ginny didn't care. She wanted to be a part of protecting their world from the onslaught of the Darkness she was convinced in her soul would overtake it with Lord Voldemort's victory.