Hmm, there seem to be a lot of books that don't have it. There isn't a box to check or something else to include it?
Of the ones showing in the "customers who viewed this item also viewed" section on her book page - none of them have the "look inside." On my view of Amazon. Yours might be different. ?
That's weird. I know that KDP has been having various issues this week (some folks on the KDP boards have reported over a week for Look Inside to show up) so maybe that's part of the problem.