Rags to Riches to Revenge

The waitress who marries into the family is not a waitress. She is the heiress to one of the country's biggest fortunes, and she takes the disguise on because the boy who saved her life when she was young might feel pressured by who she really is. She wants to repay him, so she marries him and moves into his household as an ordinary woman. His relatives treat her accordingly. She takes the insults and the slights for years without answering them. Her husband is unfaithful, and by the time he is preparing to divorce her she learns that the boy who pulled her out of danger was not him at all. It was his younger half-brother. She drops the disguise. There is the matter of the debt she still owes to the brother, and there are the years she spent being humiliated by the wrong man, and she goes after both.