The Grand Sophy by Georgette Heyer
When the redoubtable Sir Horace Stanton-Lacy is ordered to South America on Diplomatic Business he parks his only daughter Sophy on his sister in Berkeley Square. But Sophy's cousins are in a sad tangle. The heartless and tyrannical Charles is betrothed to a pedantic bluestocking almost as tiresome as himself; Cecilia is besotted with a beautiful but quite feather-brained poet; and Hubert has fallen foul of a money-lender. It looks like the Grand Sophy has arrived just in time to save them all ... The undisputed queen of historical romance shows in Grand Sophy all the wonderful storytelling that won her a huge, devoted readership, which continues to this day.