It's hard to guess without knowing her tastes, but you generally can't go wrong with the classics by companies like Chanel or Guerlain or Lauder. I would stay away from candy/gourmand types of scents because she would probably find them too juvenile. Floral Chypres would be a good bet. I'm her age and I like those.
I would take what's highlighted and suggest that if you live nearby, or will be celebrating her birthday together, perhaps accompany her to several fragrance shops, let her choose what she wants, and you buy it for her. Make an occasion of it... brunch/lunch... dinner.
Yup, all great choices! Arpege is gorgeous.Chanel is already a good starting point for classic stylish floral chypres, also adding a few more timeless choices like Silences de Jacomo, Je Reviens by Wort, Miss Dior by Dior, Arpege by Lanvin to a possible (re) testing list
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