Arthur, I agree - It does look odd. If it were extended it would be much shorter than her left arm and she doesn't seem to be sitting askew which might show as that type of distortion.
Also, I'm a bit suspicious of the white blobs and longer strokes on the bottom underskirt(?) I've not come across any portrait painter of that period making such obviously painted splodges. They look rather crude. This could, of course, be the scan/photograph as the image is very blurred.
Although I think it is an overpainting,is it possible to put up a clearer image ? **
Gadget
** or is this blurring in the copy you were sent?