I left the following comment on csprague's filmblog about The Nanny Diaries, in which she wrote "The love story was a side note, or at least it seemed that way since it was so underdeveloped."
I have to agree with you. I can't help but think that the relationship between Annie and "Harvard Hottie"/Hayden should have been more than a side story, especially given the film's conclusion. But a more intense courtship would not have fit with the overall motif of the film. Instead of striking a good balance, the love story is awkward and out-of-place.