The two sisters work out their "competition" over Peter peacefully.
Anne and Peter have a better connection than Margot and Peter do, in part because Anne is so extroverted and talkative. When Margot sees Anne and Peter have hit it off, she stops "competing" for his attention.
From the letters, we can tell that Anne looks up to Margot, although the two are not very close. At times Anne envies Margot because she feels Margot is so pretty and likable.
