> Although I'm not ENTIRELY certain what the point of expanding her roll in this movie...

It was to play up the love triangle angle a bit. It was present in the book but in a much more subdued way.

> > Wormtongue: Rocking. His slightly expanded
> >role works beautifully.
>
> How was it slightly expanded?

Wormtongue doesn't particularly have any scenes prior to Gandalf coming in and freeing Theoden. The movie adds a couple of earlier scenes that play up his part in effectively usurping the kingdom.

> Although how did Eomer's contingent of Rohirrim grow from the dozen we see initially into an entire fricking army?

I wondered that too. Earlier, when Eomer is telling Aragorn and Co. about his banishment, he mentions that 2000 other people are with him, so I assume that his particular band was only one of many travelling north. But this could have been clearer, to be sure.