Board Thread:Speculation House/@comment-26025032-20160110222427/@comment-4010415-20160110230011

Dude, episode 7 (Beginning of the End) pretty much clearly showed that Emerald's Semblance lets her make someone hallucinate whatever she wants them to hallucinate.

First, we have Cinder explaining how Emerald stole a ring from a jewelry store. She mentioned that the shop owner gave Emerald the ring and smiled, and we heard the shop owner suddenly get confused, freak out, and call for someone to catch the thief.

Then, we have this:

The difference between Emerald's and Neo's Semblances is:

Emerald makes a person hallucinate. No one else can see what her target is seeing.

Neo creates an illusion that everyone in the area can see.

Therefore, we know that Emerald made Yang halluciante Mercury attacking her. What the cameras and everyone else saw was what really and truly happened.