Lol 5 years later I respond. Anyways, I'm pretty much convinced that this Archerko is not the actual female version of Archer. I think Himura created this Archerko from Heaven's Feel ending, in which Illya sacrifices herself and he made Archerko the Heroic Spirit Illyasviel Von Einzbern.
comment #15384 Are you fucking retarded or what? Nice spoiler for the kids, while adding no information for anyone who wanted to find out.
This is the reply 10 years later. Archerko is actually Illya from Archer's timeline that diverged from Archer's own past due to 'that timeline's' Shirou being able to save Illya from dying by using the re-energized Avalon(which Saber left behind after disappearing) and transplanting some of his Magic Circuits to her body.