What dilemma is Dahlia facing in Chapter 12?

In Chapter 12, Aunt Dahlia explains that she pawned her pearl necklace in order to pay for the Morehead serial for Milady's Boudoir. Before pawning the necklace, Dahlia had a copy made so that her husband, Tom, would be none the wiser, but discovered that when Lord Sidcup arrives at Brinkley Tom will show Sidcup the necklace so that he may determine its value. Dahlia has a lot to lose if her husband finds out that she pawned her necklace.