I purchased this book in the late 1970s or early 1980s. It was about a girl who started out very poor, but whose father somehow struck it rich (gold?). I don’t seem to remember a mother. The MC made friends with a girl who was from a proper family. Maybe they met at boarding school. The MC fell in love with the friend’s brother but it was always intimated that she might be too “new money” to be suitable for him. The MC also befriended a colorful actress named, Florie or Flossie. Her advice was to be flashy and I seem to remember the phrase “plenty of ooh la la”. But gradually the MC realized that the actress might be a bit gauche. One main struggle was the MC trying to seem well-bred and not like new, flashy money. I remember scenes of the MC being fitted for and purchasing new, elegant clothes.