Olivier Milla Armstrong(オリヴィエ・ミラ・アームストロング) is the older sister of Alex Louis Armstrong and is charged with leading Briggs' Fortress, protecting the country from the neighboring country of Drachma. She is a firm believer in survival of the fittest, which earned her a reputation within the military and in Drachma, as one who should not be crossed. Her subordinates hold her in high regard as she readily joins them in hostile situations and disregards the orders of superiors if she disagrees. Her subordinates answer only to her.

Unlike her brother, who is cheerful and kindly to all around him, Olivier distrusts everyone when she first meets them, and has no patience for formalities or idle conversation. She always carries a sword at her side, and is proficient enough to be able to defeat her brother with it.

Source:Wikipedia