She isn't actual trying to take over the galaxies' species or start her own forerunner ecumine at all... [spoiler] She's actually forming her own faction for Pokemon GO. The Guardians are really just a new legendary Pokemon and this is all part of an event she set up with Nintendo. Everyone who "died" during the guardians' awakening were in reality just paid actors (Except for Ferro, that was an unfortunate series of events for which Nintendo of UNSC has already make a public apology for.) Chief was already Team Valor so Cortana tried to lock him in a Cryptum until he decided to change teams or until she could hack his account to put him in her faction. Due to her wording many have mistaken her threats as a declaration of war and conquest against the various species of the galaxy, but it has since been clarified that this was only rehersed invitation and promotional material. The battle for Auriga Station as portrayed in the map Torque was actually a coordinated effort by the UNSC to take back the Gym on that space station. People in the 26th century take Pokemon Go very seriously. [/spoiler]