It is thinner and much like Ivy's hair. It has layers in front and the braid is in a unique position on top.
Her hair has subtle caramel highlights, no where near as many as Marie Grace's wig.
Mattel Samantha's hair is much fuller, it holds a curl whereas Grace's hair is straight with a soft wave on the bottom.
Maybe here you can see the differences in thickness when the hair is gathered.
Just looking at the band wrapped around the hair once will show the difference in thickness.