Blimey! Well, all I can say is, I hope I'm still keen and alert enough to read at ninety seven - and capable of browsing round a bookshop. Good for her.

not historic fiction, but fascinating, are

My Dearest Friend : Letters of Abigail and John Adams edited by C. James Taylor and MArgaret Hogan

and
Founding Mothers : The Women Who Raised Our Nation
by Cokie Roberts

a novel that popped up when I was trying to find the editor of the letters book was:
Patriot Hearts
by Barbara Hambly
but I can't tell you anything about that one beyond the reviews: it's a novel about Abigail Adams, Martha Washington, Sally Hemings and Dolley Madison and their experience and their view "behind the scenes" of the early American national experience.

Here is a link that might be useful: Patriot Hearts reviews

I'm assuming she's read Joseph Ellis's Founding Brothers and David McCullough's John Adams? If so, have her try Founding Mothers, by Cokie Roberts. The women include Abigail Adams and Martha Washington, but also others who are lesser known now, but were well known then and who had the ears of the founding fathers.

If she hasn't read the two aforementioned books, those would be the ones I'd get.

Here is a link that might be useful: Founding Mothers: the women who raised our nation

"Undaunted Courage" by S. Ambrose (the journey westward of Lewis and Clark).

Not historical fiction, but American history: "Mayflower" by Philbrick.

I really need to wake up before I post - not only did I miss that she wanted historical fiction, but I totally missed ccr's post recommending the same book. Ah well

Ok, historical fiction - if she likes the history of early US, she must try City of Dreams by Beverly Swerling. It tells the tale of the founding and development of NY, first by the dutch, then the brits, then as an American colony. Very well written, and well researched, well worth the hefty weight of the book!

Brave Companions by McCullough is a collection of biographies of Americans whose names we recognize, and about whom we have a faint idea of why we recognize them, but we can't quite get it. He fills in the backgrounds and the details. It was one of those books where I kept finding myself saying, "AHA!".

Thank you all for these titles. I have made a list which we will take and she can pick what appeals to her most. They all sound interesting and I'm sure it'll be hard to choose just one.
If you think of any others, please continue to post. There's always the next trip to the book store.