Emma is the name of a background character who resembles Emily in appearance and dress. Her name is revealed in a What's Your Favorite Word? interview she gave when she was 11 (now 12), at which time her favorite word was "Razzle-Dazzle".
She has long black hair tied back in a ponytail and wears a blue shirt under a pink dress.
She is part of Becky's class, and sits beside Eugene a couple rows back. She and Eugene are good friends, and are often seen hanging out together.
Interview from WYFW
My favorite word is "Razzle-dazzle." It's loud, it's bright... I just like to say it all day long. Razzle-dazzle, razzle-dazzle. So many z's. Razzle-dazzle. My room is probably razzle-dazzly-ish. RAZZLE-DAZZLE!
She and Eugene are guests at Becky's 11th birthday party.
In part 4 when pointing lady and Miss Davis are watching Miss Power's hijacked news broadcast (on the right side of the screen), Eugene is standing on the far left side (to their right) and is being hugged by Emma.
Later when the pointing lady speaks up against Miss Power, Emma is standing behind her (Eugene's arm around her shoulder) beside Bampy and Great Granny May petrified as Miss Power's sidekick abducts the mother of Little Granny May.