Johnson's two free throws broke a 60-all tie and helped the second-seeded Blue Devils (27-5) avoid a three-game sweep by their fiercest rival. Duke went 6 for 6 at the foul line in the final minute of a tight game, holding off UNC freshman star Diamond DeShields and the sixth-seeded Tar Heels (24-9).
After Oderah Chidom hit two more free throws to make it 64-61 with 17.5 seconds left, DeShields launched a 3-pointer for the tie but it rattled out. Chidom got the rebound and was fouled, knocking down two more free throws with 9.2 seconds left to seal Duke's trip to Sunday's championship to face No. 2 Notre Dame.
DeShields led all scorers with 25 points. Classmates Allisha Gray had 14 points on 4-of-8 shooting from distance and Stephanie Mavunga provided 13 points and nine rebounds going up against ACC Defensive Player of the Year Elizabeth Williams, who had 12 points and nine boards before fouling out late in the second half.
North Carolina led by as many as eight points, 43-35, after DeShields capped a run of four-straight made three-pointers by the Tar Heels to open the second half. Gray had the first and her long-time friend made the next three in the first 3:13 out of halfime.
Duke rallied and cut it to 43-42 two and half minutes later and finally tied the game at 55-55 on a three from Johnson with five minutes to play.
Williams tied the game 60-60 with a little over a minute left to play off an offensive rebound put-back. She then made a key block on Mavunga at the other end that led to Johnson's deciding free throws to give the Blue Devils the victory.