The second half of the verse includes the redundancy, “She was his only child; besides her he had neither son nor daughter.” The double mention of her solitariness emphasizes Jephthah’s hopelessness: the death of his daughter would end his family line.
34 Then Jephthah came to his home at Mizpah. And behold, his daughter came out to meet him with tambourines and with dances. She was his only child; besides her he had neither son nor daughter.