Here I have parented the dress to the body, then scaled the body down to 50% Zscale on FRAME 1. The dress has AGAIN, followed the scale of the body as I keep saying it would and as you yourself have admited it would do. You are either not doing it the way you are describing or you are skipping a step in your description. I would guess that you scaled the body down at frame 1 BEFORE you parented the dress or the dress would just have scaled down with the body as shown here but you have specifically said you parent and then scale.