But i just finished a3 and the cut scene, her name is Enterprise.
And if that indeed is Enterprise, does that mean every sirens are based of her?
In the first place the Sirens leaked out the Wisdom Cube to human in order to conduct their "experiment" on alternate timelines and future possibilities (think Marvel's multiverse). But so far, every single timeline all lead to the same result, war wages on and mankind ultimately destroyed themselves.
Code G is Enterprise from a timeline where she's the sole survivor out of all ship girls. It's confirmed because you can see in her dialogue there are mention of stars in the sky and wondering if the commander will still be with ehr after the war ends which are all part of her in-game line, specifically her Affinity:Friendly and Love line.
And now she's tracing the Siren's across different timelines to go back in time and find her "original" commander who are presumably dead.