She is wearing a a lovely blanket with sleeves. A blanket with many cables. Take the amount of yarn suggested for any Twin size blanket. That should be enough yarn. Oh! I'm thinking of yarn who's thickness would need Needle Sizes between 4mm to 6mm. Knitting Worsted / Double Knit.
Since a dress will be shorter than a blanket, the yarn for a blanket would be enough to make the sleeves and cables.
Besides, do you really want to Knit L-O-N-G, long cables?
Since a dress will be shorter than a blanket, the yarn for a blanket would be enough to make the sleeves and cables.