I don't remember the Goblet of Fire ever mentioning who George took to the Yule Ball. Was it ever mentioned anywhere, or did he go alone? I don't think he went alone and just hung out with his twin, as his twin had a date.
“Who’re you going with, then?” said Ron.
“Angelina,” said Fred promptly, without a trace of embarrassment.
“What?” said Ron, taken aback. “You’ve already asked her?”
“Good point,” said Fred. He turned his head and called across the common room, “Oi! Angelina!”
Angelina, who had been chatting with Alicia Spinnet near the fire, looked over at him.
“What?” she called back.
“Want to come to the ball with me?”
Angelina gave Fred an appraising sort of look.
“All right, then,” she said, and she turned back to Alicia and carried on chatting with a bit of a grin on her face.
“There you go,” said Fred to Harry and Ron, “piece of cake.”
— Goblet of Fire, chapter 22 (The Unexpected Task)
I’m looking for an answer from the books, Pottermore or an interview that I might have overlooked. I’m not interested in an answer from the HP Wiki or the movies.