There's a fair bit about Deb Willet in Pepys's diaries; he is astonishingly explicit about his relations with her (and with other women -- besides his wife). Apparently he truly cared for Deb; he sought her out several times after his wife had forced her removal from their home (after having discovered them in flagrante delictu), and it was only as a result of an ultimatum by his wife that he ultimately stopped pursuing her.