She should be slightly worried that Vetinari knows where she lives and what she does for a living. Grace runs a pet-food shop on Pelicool Steps and in her spare time appears to have an inexhaustible passion for all kinds of general knowledge trivia. As one of only five people in Ankh-Morpork who could confidently and correctly answer the question "What is, or are, Pysdxes?" (the others are Vetinari, Drumknott, "Puzzler" of the Times and the Curator of Ephebian Antiquities at the Royal Art Museum), Vetinari is concerned that somebody with a mind like that might not just be content to run a pet-food shop. Therefore she is under observation...
In Unseen Academicals, she briefly employed Rudolph Scattering, but he left after three days because the way the kittens stared at him gave him nightmares. The world can be very cruel to some people... Vetinari's mild obsession with her intellectual ability extends very clearly into Unseen Academicals as well. Are we being set up for something here?
In Raising Steam, the word is lagniappe1: not too taxing, at least for anyone familiar with Genua, but it seems to provoke a change of puzzle-setters at the Times. Can one accuse a graduate of the College of Assassins of poor sportsmanship?
1 Literally a small bonus, a little extra to make the deal, but taking on the suggestion of a bribe.