The little lady agency and the prince / Hester Browne.

Enhanced descriptions from Syndetics:

Hester Browne created a unique heroine in Melissa Romney-Jones a.k.a. Honey, London's ultimate freelance girlfriend, who won the hearts of readers on both sides of the Atlantic in her "charming and feel-good"(Cosmopolitan) and "funny and original" (People) earlier adventures. Now herNew York Timesbestselling series sparkles brighter than ever as irrepressible Melissa is hired to reform a playboy prince -- and finds she could get used to the royal treatment.Making plans for her wedding to American fiancé Jonathan Riley, who now runs a prestigious Parisian real estate company, Melissa agrees to do a favor for her beloved grandmother: transform the notorious Prince Nicolas von Helsing-Alexandros into a proper gentleman for the sake of preserving a family inheritance. Even possessive Jonathan agrees it's a great opportunity to make social connections. But taming a prince might prove too big a professional challenge for Melissa when she's confronting so many seismic changes in her own personal life.Jonathan needs her in Paris. Her sister Emery's newborn son needs a christening ceremony, as well as a proper name. Emery herself needs Melissa -- to protect her from their bulldog nanny who's returned to do much more than babysit. Most unsettling of all, Nelson needs her to find him a new flatmate because she'll be moving out soon. Balancing all this with late-night dinners, polo matches, and a Mediterranean cruise with Prince Nicky, who is as charming as he is exasperating, suddenly has bride-to-be Melissa dreaming of a fairy-tale ending -- and not the one she expected!