Passion’s Legacy by Lori A. Paige

A passionate love story, set in pre-Victorian England. Sarah Lindsay, in refusing the marriage her guardian uncle has arranged with a man she despises, pays a steep price: she learns the stunning truth about her birth.
In confusion and despair, she leaves her guardian's home, and is rescued by a formidable Lady August Pym, who invites Sarah to her estate.
Most astonighing of all her discoveries, Sarah discovers the uncharted erotic depths in herself