House of Water — Elizabeth Renier

Frances Trelawnay was a chameleon, beautiful and unpredictable; her angelic face hid a restless and determined spirit. Secure in her popularity and her social position she once again meets Sir Robert Veryan, whom she loved when he was a gawky adolescent. Now Sir Roberts has cut a brilliant swath through English society and Frances realizes that she still loves him.
However, his seemingly ruthless pursuit of money and power and the added obstacle of his bethrotal to another woman seem insurmountable barriers to Frances.

In a whirlwind series of events the resolute young beauty risks the stigma of indiscretion to steal the affections of a man who belongs to another woman.