The website Ephemeral New York is terrific for all sorts of interesting New York history: https://ephemeralnewyork.wordpress.com (the New Year's day post is where I found the reference to her diary)

And the Historical Atlas of New York City is both visually and textually superb for all sorts of fascinating details of New York's development: http://www.amazon.com/Historical-Atlas-New-York-City/dp/0805...

Finally, "Letters of Note" has great finds from historical letters throughout history: http://www.lettersofnote.com/