After his vow, who was the first to come out of Jephthah's house to greet him?

Answer: His only daughter

She came out with tambourines and dancing. She was his only child, and Jephthah tore his clothes in grief.

“And when Jephthah returned home to Mizpah, there was his daughter coming out to meet him with tambourines and dancing! She was his only child; he had no son or daughter besides her.”— Judges 11:34 (BSB)