Alastair Laing has kindly confirmed the attribution to Boucher on examining the drawing.
Although Michel's engraving shows the figure in a carefully delineated setting, this seems not to have been designed by Boucher but added by the engraver. This relationship between drawing and print is also seen in the pendant to the present sheet, a red chalk female nude formerly in the J.P. Heseltine Collection, London (A. Ananoff, L'oeuvre dessiné de François Boucher, Paris, 1966, no. 464, pl. 88), which is preparatory to Michel's engraving entitled Venus sortant du Bain (Jean-Richard 1425).