Her Reasons

Her Reasons is a hero quest in Xenoblade Chronicles 3. It can be received by heading for the quest marker at Dies Arch, West of Zem's Crossway, after departing Colony 4. Completing it will make Alexandria available as a Hero.

Quest Events
Her Reasons is divided into multiple quest events leading to the main quest:
 * Alexandria's ambush at Dies Arch
 * Fight Team Rhyza at Bittley Slope
 * Fight Team Chelle at Lisza Garden
 * Fight Team Fili at Fetos Sandgarden
 * Fight Team Sequoia at the Great Cotte Falls, just beyond the Urayan Tunnels
 * Attack Colony Iota (Her Reasons main quest)

If the party is under level 40 during Alexandria's ambush, the game will recommend to defeat the commando leaders first. If the party is at least level 40, the game will recommend directly attacking Colony Iota. Both options are available to the player no matter the initial script.
 * If Colony Iota is attacked first, Rhyza, Chelle, Fili and Sequoia will be fighting alongside Alexandria. It isn't required to defeat them to complete the quest.
 * If the commando leaders are attacked first, Alexandria will fight without those who have been defeated. It isn't required to defeat every commando leader to attack Colony Iota.

Result
"The party bore witness to Alexandria's ingenuity for survival and got a glimpse of her situation. They agree to keep her being a sixth-termer top-secret."