http://www.jenleheny.com/pillowcase-dress-instructions
http://www.youtube.com/watch?v=QtuGUB-jsH8
Here are a couple of links to help you explain it to her. The You Tube video seems very helpful.
If she is looking for a very simple starter project you might want to consider some the pre-smocked fabrics for sale right now. The have beautiful spring colors. One straight seam and two straps and you'd have a cute sundress.
Good luck!