The Daughters of Blane — Harriet Smart

Three young ladies with more beauty and charm than Isobel, Leonora and Vivien Buchanan, daughters of the laird of Blane, would be hard to find; their marriage prospects are exceptional. Indeed, in the summer of 1890, Isobel is already engaged to a duke.
But Isobel is secretly uncertain about the man she is to marry. When another, utterly unsuitable candidate presents himself, she is stunned by the strength of her feelings. Suddenly she must make a decision that could have devastating consequences.
Younger and more independent, Vivien has always resisted the destiny allotted to women of her class. Marriage to a radical politician seems to offer her the deep and close relationship she seeks; but time and changing ideals can temper the deepest passion.
Only Leonora, spoiled and extravagant, is ready to settle for a conventional marriage. But a rich and titled husband is no guarantee of happiness, especially against the pull of true but illicit love.
Set against the turbulent events of the 1890s and moving from the Western Isles of Scotland to London society, from slum life in Edinburgh to a palazzo in Venice, and finally to the battlefields of the Boer war, The Daughters of Blane is the passionate and ultimately triumphant story of three women who refuse to fit the mould society has made for them.