I think there is a third option, that Ann Gordon, the mother of Richard Dickens, isn't the daughter of George Gordon, with Annabella Stewart or any other woman. She definitely isn't mentioned in The Scots Peerage, volume 4, pages 529-531.
RJ is also right, in that Annabella Stewart seems to have far too many children. It isn't clear who was the mother of most of George Gordon's daughters, but I think only 1 daughter has been attributed to Annabella Stewart.