I always thought it wrong that J.K. Rowling didn't show George's reaction to Fred's death. It must be hard for George. This story just shows something that I think George could be going through soon after Fred's death. There are no pairings in this.
George looked at himself in the mirror and saw Fred staring back. That's just how it is that's how it will always be because they're one and the same. One soul born into two separate bodies. Two halves of a whole. But George knows that when Fred looks in a mirror he doesn't see George; and he doesn't see himself. He doesn't see anything, because George knows that Fred will never look into a mirror again.
George stands in front of the full mirror hanging in their, no, his room. George gets his own room now he doesn't have to share. He remembers when he was younger he would complain to his mum. Everyone else got their own room. Why is it that George always had to share his room, and all his stuff? George remembers a time when he would have given anything to just be his own person, and not have to share. Now George would give anything to share with someone. To share his room, his stuff, his face. So now George just stands there looking it the mirror at the face he has shared for so long.
George is wearing a hat to cover his ears. Fred has both of his ears so shouldn't George too? They do share everything after all. Fred is staring back at him from the mirror with his hat covering both his ears just as it should. His red hair is poking out from the hat at odd angles. He is wearing a dress robe at his mum's insistence. George feels ridiculous in the monkey suit and sees no reason to wear it. George's face softly turns into a smirk and he is happy to see Fred's face mirror his own in a smirk in agreement over the ugly robe. Fred never liked dressing up.
George stands smirking at Fred through the mirror only letting his smirk fall off his face when he hears his mum yelling up the stairs for him. Not George and Fred but just George. His mom always yelled for both of them that's how it always was. George nods at Fred in the mirror and goes down to meet his mother. She is there waiting for him, after a quick word from her about how handsome he looks, she takes his hand and George can feel himself being pulled to a new location.
George and his mother appear on a grassy hill covered in strange stones. George can make out a group of people on the top of the hill their red hair blowing in the breeze. He feels himself being pulled towards them. As he approaches he sees them gathering around one of the many stones. George pushed through the kneeling next to the stone. George can only make out two words through his eyes before the rest become blurry, but those two words were enough to break him. Those two words looked so alone etched into the stone without George there with them. They were enough to prove that Fred would never see George through the mirror again. Those two words changed George's life forever. Fred Weasley.