I routinely buy quinoa, as well as somewhat more obscure things, such as mayocoba beans and Salsa Lizano. I own two pressure cookers - a search of my e-mail history will show me asking my sister for a recommendation, followed by a purchase from Amazon. When my decade+-old computer backpack gave out, I asked my friends for recommendations.
Bla bla correlation and causation. I did not infere that ALL users whom exhibited the same online behavior got the same search. Other factors led the cops to the premises. To me the point was, yes they are looking at your search history. But as other users have pointed out, her husband could have been included in a 3-degrees of separation blanket warrant.
tl;dr: It was a former employer of her son or husband who called the local cops because of searches for "pressure cooker bombs" and "backpacks" in a work computer's browser history.
No FBI yet.