Or even much much older:

"Figurines produced by the Vinča culture (c. 5700–4500 BC) have been interpreted by archaeologists as representing women in miniskirt-like garments"

Her own Wikipedia page questions the association. Her focus was more on a specific style of minidress (mostly the iconic Mod fashion minidress).

https://en.wikipedia.org/wiki/Mary_Quant#Quant_and_the_minis...