It’s White (Adam) to play. He can force the draw with 81. Rc1, but instead played Ke6, which loses.
Had he played Rc1, the game might have continued: 81… Kb5 82. Ke6 Rd2 83. Kf5 c4 (or Kb4) 84. Kxg5 Kb4 (c4), drawing.
But after 81. Ke6, the game continued … c4 82. Rc1 Rc5 83. Kf6 Kb5 84. Rb1+ Ka4 85. Ke6 c3 and Adam resigned after a further four moves.
After four rounds, Monika was joint leader on four points, but lost in the fifth round. Adam, doubtless exhausted and probably deflated after that struggle, went on to lose to a lower-rated opponent in Round 3 and only drew in Round 4 with another lower-rated player.
Needing another 22 rating points for his FIDE Master title, Adam (on 2½/5) now faces an uphill battle, having lost 45 points after five rounds. He has four more rounds to claw back the deficit. Today he faces yet another opponent rated more than 200 points below him, where even a win will gain him only nine points.
You can follow his progress here.