Out of curiosity, I looked into how Billie actually came up with her fragrance.
I was quite surprised by her statements, as I can somehow totally relate:
The scent reminds her of her old childhood room in her parents' house.
According to her, it originated from her wardrobe, particularly from a net top that she often wore to parties in her youth.
Thinking about the fact that I am smelling a net top that teenage Billie wore, the scent has completely changed in my nose.
It still smells as lovely powdery sugar/vanilla as before, but I always have an image of a net top in my head.