I thought Emma was pretty good, actually. She has a comfort and a familiarity with the role, and sang and danced it quite fine. I think the one thing that video continues to show, is that the younger they go in casting the role, the less of a fit it is with the character. Similar to what Ermengarde says, it's a lived in role. It's not meant to be played by an ingenue. Emma is typical of what happens when they go young, the Roxie monologue is chirpy and light, when for example Pamela, she was able to channel a whole lot into that moment.
As for Emma, she'll be a fine in-between and tour Roxie.
"Hey little girls, look at all the men in shiny shirts and no wives!" - Jackie Hoffman, Xanadu, 19 Feb 2008