I think you're making the bear with instructions on page 33. (The directions for this bear is a bit different than the one I made, photo pg. 27) If this isn't the pattern, let me know!
I would sew the seams of the body like instructions say. Take a look and see if in fact the seams should be centre back and front or on the sides. She may want the seams down the centre back and front because of the way the arms and legs are attached to the body. They move! There would probably be less stress on the knitted piece if the limbs weren't sewn to a seam. (Somebody correct me if I'm wrong!)
You do leave the cast off edge open because you're going to run a gathering stitch on this edge and draw it in after you stuff it. (I embroidered the face before I fully stuffed and closed the head.)
Your photo isn't appearing on the screen, but I didn't have the triangular pieces at the bottom. The only thing that I can think of is that it becomes the bear's crotch??? The hip? Now I'm curious, but it may become more evident as to how to construct this bear once you start.
That is a darling pattern you chose. What color are you making the bunny sleeper?
Good luck. Let us know how you make out.