I have only seen one modern "toy" sewing machine that really has potential to encourage a new little seamstress. It is a Hello Kitty machine by Janome -
http://www.target.com/Hello-Kitty-Se.../dp/B000B8WSJ2 It's actually quite a competent little machine and not a toy at all. :)
You can buy a similar machine without the Hello Kitty coloration -
http://cgi.ebay.com/160634372459
Adult quilters buy these tiny machines for classes and such.
Most chainstitch sewing machines are so frustrating to operate that they can turn a child off of sewing. You at least want the machine to sew a decent seam. These have several different stitches and take ordinary feet and accessories. Plus they sew slowly, so that a child won't be intimidated.
I bought the Sew Mini for my granddaughter because she was scared of her mom's big machine - she feels more confidence with this one and that's important for someone learning a new skill. :)