How does the author use foreshadowing in Crocodile on the Sandbank?

From the text:

"I experienced a revelation in that moment. I wanted Walter for Evelyn. They were ideally suited; he was an honorable, lovable young fellow, who would treat her well. If I had to give her up, I would not repine seeing her in the tender care of a man like Walter. I determined, in that instant, that it should come to pass. But I foresaw that it would take some effort, even for me."