Presumably the blue sky was blown out. Yes? It would be interesting to see when we have the Aperture plug-in combining the two different shots for greater dynamic range. In any case a great shot!
That is a good lens but this picture is not what it should be on a technical level. I would have kept the same shutter speed but used maybe the full 2.8 and with ISO settings worried about exposure. Watch your focus, it's behind her. That is a tricky lens but will in time give you great results.
*****
Yes, all good points. I would definitely NOT have used those settings today and suprised i used them then! I would venture to guess camera was left on Manual from some previous shot and not changed when it should have been.