Didn't expect this one, did we? We have no idea when or where she wears this dress.
We can't pin down the fabric, or even the color, really, because of the lighting. Looks like a dark gray, possibly greenish gray, but it could be a plum color, it's hard to tell. Looks heavy, possibly a wool, maybe a wool felt.
The scoop neck is bordered in a wide band of embroidered fabric or brocade—looks like a leaf pattern. We can just see about ten vertical pintucks or pleats just below the band.
Could it be something more like a cloak or a coat than a dress? (If it is, those could be pleats rather than pintucks.) Just look at the way it's folding and draping below the shoulders. Either that or the shoulder seams are dropped—we might be seeing one dropped off her right shoulder.