I'm looking for a Harlequin/Silhoutte book from the late '80's early '90's set in Chicago about a medical resident named Anna falling in love with the chief surgeon--she also does modelling on the side for extra money

Call your public library's reader's advisory desk. There are references in print and a databases (plus Google searches) for locating the title. I did a cursory search, but had no luck. The Harlequin site and Amazon will allow keyword searches for older titles.