I agree, it's a fine shot with nice even light. If I was to nitpic I would prefer if her glasses could have been lifted a little higher on her face rather than having the rims just covering part of the eyes.
I agree with Tom about the glasses, but love, love, love the pearls - they echo her smile. That reminds me of the self portraits by Rembrandt, where the edge of his hat would do likewise.
Excellent Hamish, I am not fully convinced about mentioned glasses, it still works for me in a less than conventional way. As is, makes it as it is, a superb portrait. Beautiful processing