This is always a question you should consider when you read a story, especially a story that you are reading with a critical eye. It is one of the first choices an author has to make -- "Who is going to tell this story?"
In this story, there are actually several stories, and the point of view is third person for each one. The fact that the narrator is omnscient (can relate the attitudes and perspectives of all the characters) is also a choice that affects the reading. What is most interesting about this narrator in THIS story is that the third person narrator seems to actually be the author/writer of the stories being told. The narrator speaks directly to the reader before story A and says, "If you want a happy ending, try A." The narrator is telling the reader what to think and previewing what to expect. As the actual story changes through forms A, B, C, D, E, and F, the narrator remains third person -- the author still seems to be very much "in charge" of the telling. The final few, brief paragraphs have the narrator/author step out the fiction of the stories and back to the stance of writer explaining the writing process, yet it is ultimately still part of the story untitled "Happy Endings" by Margaret Atwood. Our response to the story is affected by how we understand that narrator's tone and what those stories are about. We understand Atwood's intention to write a sort of meta-fiction, and we understand her theme about both love/relationships AND the writing process in general.