The artist clearly shows the bobbins and pins, and also the pricking card and the lacemaking pillow (or 'cookie', as it is nowadays sometimes called). From these details it seems she is making a relatively small piece or band of lace.
The sitter is wearing a yellow garment with a lace collar. The cushion to the left is a sewing cushion (naaikussen), which was made of a rigid material covered with fabric. It contained various compartments for sewing tools and materials.
Detail of Vermeer's The Lacemaker. Copyright Jonathan Janson.
See also the TRC Needles entry on Het Straatje van Vermeer.
Digital source (Jonathan Janson; retrieved 1 July 2016).
Musée du Louvre online catalogue (retrieved 1 July 2016).
WV