Constantinou's Mistress

Description for CONSTANTINOU'S MISTRESS by Cathy Williams:

Lucy Reid had a crush on her boss, Nick Constantinou. Then one evening while working late, her dreams came true -- Nick arrived at the office unexpectedly and, before they knew it, passion had taken over!

Now that Nick had discovered what lay beneath Lucy's efficient exterior, he could think of nothing else! However, despite his growing feelings for Lucy, he was unprepared for her shocking news....

This is Harlequin Presents #2340, August 2003.