I've always taken Cordelia's remarks about her social ineptness to be of a piece with her remark about being a late bloomer--that she spend a lot of her young adult-hood as the social ugly duckling before finally finding her stride. By the time we see her in Shards, she seems to have grown into herself, which makes her later amazing-ness less jarring for me.

Actually, that also suggests the somewhat alarming thought that what she really needed to shine was a challenge... a challenge on the scale of Barrayar.