What’s the probable relationship between the two speakers? What does the woman mean?

W: Need I take some medicine?
M: Yes. And I strongly advise you to go on a low-fat diet.
W: Do you really think that’s really important?
M: Of course. If you don’t, you might have a heart attack some day.
W: Well, I think I should follow your advice. You have been very helpful. Thanks.

M: Hi, Susan! Have you finished reading the book Professor Johnson recommended?
W: Oh, I haven’t read it through the way I read a novel. I just read a few chapters which interested me.