I would say Jane Austen implored the girl to marry only for love in a logical way so that if she really truly loved the man and knew that was the case after examining herself and her feelings carefully, then she should feel that it was a good decision to make and carry through with it.
The narrator is not happy that he has been tricked into Simon Wheeler's story-telling antics. He is annoyed that he is stuck listening to these tales about Smiley's gambling. While he listens well, he is not amused, patient, or attentive.
