(Edited to add the picture. Helps to show the trouble if I need feedback, eh?)
Well, I did not look closely enough to determine whether there was a noticeable difference between the original yarn and the additional yarn for completing the piece. However, it took less than one repeat of the edging chart to see what I could not see before. You can see it, too, can't you? Somewhere in my brain, I must have known this to be true, as I had already been thinking of alternate plans for the yarn. While I am a little sad about this, this does free me up to pursue other projects. Still, I'm not quite sure. I might knit on this a little more before making a final decision.