[ksen]

I could see playing Arwen up in the first movie to draw the ladies in to see it. But you'd think that they wouldn't need to do that anymore since whoever saw FoTR will most likely be coming back to see TTT and RoTK no matter who is prominent on the poster.

[Overtaxed]

IMHO the only reason Arwen needed a built-up part is so that everyone would "get" the Aragorn/Eowyn thing. It doesn't need anything beyond that.