The Absentee by Maria Edgeworth

Lord Colambre finds that his mother Lady Clonbrony's attempts to buy her way into the high society of London are only ridiculed, while his father, Lord Clonbrony, is in serious debt as a result of his wife's lifestyle. His mother wishes him to marry an heiress, Miss Broadhurst, who is a friend of Grace Nugent. However, Colambre has already fallen in love with his cousin, Grace Nugent, who lives with the family as a companion to Lady Clonbrony. Worried that his mother will pressure him into a marriage with someone he does not love, Colambre decides to leave the London social scene and visit his ancestral home in County Wicklow in Ireland.