Verified answer

Try looking at the official website - or look on the credits when the film comes out!

Extras don't get credited at the end of a film and they don't get credited on any website either.

I don't think you're going to be able to find a list of the thousands of extras in that film. And if you only know her first name, chances are theres at least a couple people with her same name (unless its some crazy name like Likapoopahooma).