Oh, gawd, I'm torn between trying to make you feel better and telling you what I really think of her. It be the latter I'm afraid, I think you've been completely ripped off. It looks awful, sorry.
You must be devastated you've got this on your plate with just over a week to go, can't imagine how stressful that must be.
Can you contact this woman? I would go to a shop tomorrow and look at off the rack dresses, also check monsoon and Biba and the like. I'd fight for a full refund off this 'dressmaker' as she's took the p*ss good and proper.
Hope you sort something soon and get a dress you're happy with. Goodluck.