However, maybe it says something about one of her favourite maxims, namely "Seven years would be insufficient to make some people acquainted with each other, and seven days are more than enough for others."

Despite Marianne's insistence that she is "much better acquainted with him, than [she is] with any other creature in the world" (excepting her mother and Elinor, and despite her assertion that "At my time of life, opinions are tolerably fixed. It is not likely that I should now see or hear anything to change them,"--she may want to rethink all of that.