Yeah, I was kind of annoyed too, but Robb in the second book was kind of a secondary character and Jeyne was introduced kind of suddenly too. I like that the directors choose to deepen Robb's story. That way his love will make the "consequences" (Red Wedding) even more powerful in the thrird season and they made Robb a more main character. Adding Jeyne in the middle of a war would have been wierd so Talisa it is then
At least her appearence makes sense in the battlefield xD