Last I checked, this character's cosplay outfit was available at Milanoo.
September is at an average level when it comes to combat, but then she excels more on aim (even more than April). September's weapons are M14 rifles with M7 bayonets. She seems to dress as a maid in mostly black with some white. She finds that Marciano isn't looking for the best robot's, but only her own. In episode 3, September dies at the hands of a man named "Swamp". Here's how it happened....
Marciano's 12 SISTERs were ambushing Mister and Swamp. Mister and Swamp were killing people, when all of a sudden someone tried to shoot them... and it was September! So September tries to shoot Mister, but he jumps out of the way and Swamp runs up to her with his gun and tried hitting her with it, but missed because September flipped over (like what cheerleaders do). So then Swamp tries running up to her and hitting her with his gun, but September ends up blocking that hit with her gun, tilting her over.
September quickly kicked him over her and Swamp fell backwards. September stands back up, but Mister comes out of no where and shoots her shoulder (but it didn't do anything since she's a robot). Then Swamp throws a bomb, except September jumps out of the way. A few minutes later, Mister and Swamp board their ship as September went into her's. Then Mister started to shoot rockets and other stuff at Marciano's 12 SISTERs' ships... but it hit September instead.