User blog comment:HalointheSkye/Volume 3 Chapter 9 Teaser - This is bad.../@comment-26397825-20160114005039/@comment-27121579-20160114114840

Cinder wouldn't try intervening at all. Ruby's seen her many different times before (enough for her to actually figure who she is, dammit!) so for her to come out in the open in the middle of the fight would make it worse. Cinder's a more of behind-the-scenes "evil-master-lord-to-this-plan" kinda type.

As for Neo - who knows where she is right now? Neo wasn't in the room when Cinder was addressing Emerald about "making sure the next round goes as smoothly" at the end of Chapter 7, so she could be anywhere really.