I can't remember the book or character names, but it was a novel from the 1850s-1950s, probably British. The main character was a very beautiful teenage girl from a poor background, with a drunkard father, who lived in the countryside in a very poor state. Later her dead mother's lover, who was a lord, adopted her and gave her a new life. Later she fell for her adoptive father's son, but they broke up due to the confusion of being half siblings, but later found out they're not?
It had lords in it, seemed British with wealthy people and families. I think it was part of a series with other novels.