I think it was from the 50s but I’m not sure
One possibility is Billy Wilder’s classic film Sunset Blvd. , released in 1950. Gloria Swanson played Norma Desmond, an aging, delusional, has-been silent film star who moves a struggling young writer (played by William Holden) into her decaying mansion to help her write a new film that will be her “big comeback”. He isn’t so much her assistant, however. More like a gigolo. She showers him with flashy clothes and other gifts in return for his affection. Does any of this sound like the film you are looking for?