Monnier was a French socialite from a well-respected, conservative bourgeoisie family in Poitiers of old noble origins.

She was renowned for her physical beauty and attracted many potential suitors for marriage.

In 1874, at the age of 25, she desired to marry an older lawyer who was not to her mother Louise's liking; she argued that her daughter could not marry a "penniless lawyer".

Her disapproving mother, angered by her daughter's defiance, locked her in a tiny, dark room in the attic of their home, where she kept her secluded for 25 years.

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