"since that adventurous girlhood in Indo-China"

 Indo-China is a region in South East Asia which was colonised by the French in the 19th and 20th Centuries.  Initially it consisted of a federation of four areas, formed in 1887: Tonkin, Annam and Cochinchina (North, Central and South Vietnam respectively), and Cambodia.  The country of Laos became included in 1893. 

Indo-Chinese Tiger
Creative Commons Attribution Share AlikeIndo-Chinese Tiger - Credit: Ltshears

Our narrator’s mother is described as the daughter of a tea-planter; the French began to survey areas where tea was grown from the 1880s and soon established a number of plantations.  The terrain and wildlife would have appeared suitably exotic when viewed from fin de siècle Paris; the mention of a man-eating tiger reinforces this.  French control of Indo-China ended in 1954, with the signing of the Geneva Agreements.