From a mathematical point of view, as interesting as a circle will be, the VOLUME of work involved is much greater, assuming the diameter of this circle is large enough that when the shawl is folded it stays put over her shoulders with the extra length down across her chest. Contrast this to a rectangle of the dimensions to go around the shoulders and stay in place because of the weight down the front. If you want this to get to the party of the first part sooner rather than later, a simple and elegant rectangle design might be best.

I really like the suggestion of a dark charcoal gray. It goes with everything. But I still have a few skeins of yarn here if you want to do a crazy-quilt kind of shawl.

SRS