If you are familiar with A Christmas Carol, Ellie is playing Belle – young Scrooge's fiancée – in this new version starring Johnny Depp, whose presence at this premiere I am ignoring. (Wikipedia calls this iteration of the story a "Gothic dark fantasy black comedy-thriller film," which is like 80% of the genres that even exist in the world. I guess they could have also made it a musical?)
This Valentino look is amazing in the sense that I am amazed that it exists. It's like Christmas at the Last Chance Saloon, where the annual holiday party always gets broken up by a shoot-out after Wild Bill accidentally drinks the last of the mulled wine.