i agree, at 3 she wouldnt really mean what she is saying about your new baby....maybe if you start talking really positively about this new baby, how she can help, how she can be a part of its life, her attitude will change....but yeah, i dont think the crossed arms and cranky attitude will last long. As soon as she sees her lil brother, im sure she will be fighting for cuddles......

ETA: sounds like a typical 3 yr old to me.....

Good luck !