Er, no. Agamemnon's stealing away of Akhilleus' prize (which just happened to be a woman) thus in the value system of the time diminishing his honour in the eyes of his fellow warriors, and Akhilleus' understandable if extreme wrath at this - *that* is the central motivation of the plot.

In Homer, Briseis is pretty much a cipher, though she does have a few nice moments. In the film she was conflated, cleverly, with Chryseis, and naturally her part is padded out hugely to give her a more personal, human relationship with Akhilleus. As I say, this was only to be expected in a Hollywood movie, and I was pretty resigned to it ;-)