She let the letter fall to the dusty ground. The picture slipped out and lay there, eyes laughing up at her, mocking her for having such silly feelings. Her hair changed to black - wild and waving around her face - and for a second the bones in her cheeks became more masculine. Then her shoulders began to shake and, as her hair transformed to dull brown, tears fell unchecked from her eyes. Everything seemed so foolish. So meaningless, so childish. She was a replacement. That much was clear to her now.
Tonks moved to the window, gazing out into the rain she noticed two swans flying against the wind. Swans. Her mother had told her once that swans mated for life. It was like another stab to her heart. Every kiss had been a mistake to him, every word a lie. His life had begun before hers, there was a whole world of secrets and love that she had never been included in. Their lost love re-found only to be snatched away again, and then she came in, a lonely girl to be pitied by an even lonelier man. A caricature of a marriage, built on unrequited love, or worse family resemblance.
No! She refused to give in. She was here, alive and his wife. She was going to have his child! She loved him. The wind whistled through the crack in the glass pane, 'replacement'. When he got she would ask him about the letter, and the horrible hateful picture. He would laugh and say it was a joke, or he would sit down and tell her she mattered more than he ever did.
In the end Remus did neither. He found the letter on the floor and the picture of his now dead lover, he left. When he returned, he apologised for leaving, but he offered no explanation and Tonk's never asked. They both knew the reason. A million things were left unsaid. He never forgave himself for leaving, and she never forgave him for loving her cousin.
So...what do you think? First attempt at a fan fic so please be kind :)