If this is Anne Sackville, her article in thepeerage is here. If this is Frances Prinne, her article in thepeerage is here.
From nationaltrustcollections.org.uk/object/486187; the carpet in the lower right corner has a discontinuity caused by suppressing a navigational mark using Photoshop.
Little detail can be teased out about this Lady's dress, but her low-heeled shoes can be seen as can the lace that looks like reticella, but appears to be more sophisticated. The black material is actually embroidered with silver or white.