Answer:
she liked the house because there was a part in the story somewhere in the beginning where Noah and her were trying to make love but somehow interrupted by their friend because Allie's parents were looking for her. in this part of the story Noah promised his dream to Allie that he will make that abandoned house theirs when they married and that's the place where they will grow old and raise their children. Even though Allie got separated from Noah when her parents took her back to the city, Noah pursued the dream and rebuilt a new house in that location and made it a really beautiful house.