To your Zack and Deus point that's not necessarily true...
We know Zack hadn't recovered enough to sue his ability let alone fight, there's a chance that he wouldn't have been able to detect that Nyx betrayed them.
As for Deus well, he's fucking Deus. There's an INCREDIBLE chance he WANTS Ella to succeed. In fact he was conveniently noted to avoid the meeting discussing what they knew about Ella due to, night terrors...NIGHT terrors...the same man who whooped a Beyond Lvl 5 at Lvl 4 couldn't sit at a table because he had a bwad dweam, fuck off.
As for the Red Energy thing that's a good point! But there's also just a chance that her Death Move is a different color just to signify it's difference or potency? Who knows, do we have any other instances where a character's Energy has changed color due to a move or action different to their usual?