At move 28, they reached the following position:
Hou Yifan - Humpy Koneru,
Women's World Chess Championship, Round 5.1 (2010)
Position after 28.Kxd3
Hou has a large advantage here. The pawn formation is the classic one from the Ruy Lopez Exchange Variation (although, as mentioned above, this game actually started as a Ruy Lopez Berlin Defense), where White has a mobile pawn majority on the kingside while Black's queenside pawn majority is useless because of the doubled c-pawns. Here Black might appear to have some compensation because White's kingside pawns are on the same color as her bishop, but White can (and, indeed must) advance those pawns so her bishop is by no means "bad."
More important is the difference in king activity: White's king can take up a powerful position in the middle of the board, while Black's is stuck on the 7th and 8th ranks, in part because of her earlier mistake 25...g6?, blocking the king's path from f7-g6-f5. Black may already be lost but at the very least she is in for a long and painful defense.
28...Be7 29.Be3 c5 30.Ke4 b6 31.Kf3 Bf8 32.g4
Position after 32.g4
White needs to open up the position to invade with her pieces and the queenside and center are closed. She also needs to make something of her extra pawn on the kingside, of course. She doesn't play h3 followed by g4, however, because that would make it harder for her king to advance.
32...Be7 (32...hxg4 33.Kxg4 is easy for White because Black cannot use the bishop to protect the queenside pawns, as she does in the game. Either White will start picking up the queenside pawns, or the bishops will get exchanged, either way with a simple win for White. Thus 33...Be7 34.Bf2 Bd8 35.Bh4 Bxh4 36.Kxh4 c6 37.Kg5 Kg7 38.h4 +-
If instead 33...Bg7 34.Bf2 Bf8 35.Bh4 Ke8 36.Bf6 Bh6 37.h4 Kd7 38.Bg5 Bf8 39.h5 gxh5+ 40.Kxh5 Ke8 41.Kg6 +-)
33.Kg3 c6 34.Kh3
Position after 34.Kh3
Now that she is ready to set up her defensive formation with the bishop on c7, Black ought to play 34...hxg4 (or 35...hxg4 on the next move). Then there could follow 35.Kxg4 Bd8 36.Bf2 Bc7 37.Bh4 Kf8 38.Bf6 Kf7, reaching the same position that arrives in the game line after move 38 (and 40). But Black would thereby avoid a strong alternative that White missed on move 36.
34...Bd8 35.Bf2 Bc7?! 36.Bh4?!
(36.gxh5! gxh5 37.Bh4, with the idea that Black cannot successfully defend against White's three threats: taking on h5, capturing on b6 with the bishop, and gaining a passed pawn with f5. A sample line:
37...Kg6 38.Kg3 Kf5 39.Kf3 Kg6 40.Ke4 Kg7 41.f5 Kf7 42.Bf6 exf5+ 43.Kxf5 +-
The h-pawn will fall, leaving White with two passed pawns.)
36...hxg4+ 37.Kxg4 Kg7 38.Bf6+ Kf7 39.Bh4 (repeating moves to reach the time control) Kg7 40.Bf6+ Kf7 41.Kg5
Position after 41.Kg5
(Black is now in semi-zugzwang. If the king moves, the g-pawn falls. And if 41...Bb8 42.Bd8 Ba7 43.Bc7 Kg7 44.h3 Kf7 45.Kh6 +-)
41...b5 42.Kh6 bxa4 43.bxa4 Bb6
We are now at the key moment in the game. Hou plays what she thinks is a winning move, but there is a flaw in her calculations.
Position after 44.Be7?
A spectacular move, but one that gives up the win. Hou had the right idea, but as indicated in the Chessbase report, she should have advanced her h-pawn first. Thus 44.h4! Bc7 45.Bg5! wins. 45...Bb6 46.Be7! Kxe7 47.Kxg6 and the Black bishop cannot get around to stop the h-pawn: 47...Kf8 48.h5 Bd8 49.h6 Kg8 50.h7+ Kh8 51.Kf7 Kxh7 52.Kxe6 Kg7 53.Kd7 Bh4 54.f5+-
Koneru, in her turn, doesn't see the flaw in Hou's calculations. 44...Kxe7! draws, as shown in the Chessbase report: 45.Kxg6 Bd8 46.h4 Kf8 47.h5 Kg8 48.h6 (48.f5 exf5 49.Kxf5 Kg7 50.Ke6 Bc7=) 48...Bh4! 49.h7+ Kh8 50.Kf7 Kxh7 51.Kxe6 Kg7 52.Kd7 Kf8 53.f5 (53.Kxc6 Bg3 54.Kxc5 Bxf4=) 53...Bg3 54.e6 Bh4 55.Kxc6 Kg7! 56.Kxc5 (56.Kd7 Kf8; 56.Kb5 Kf6 57.Kxa5 Kxf5 58.Kb6 Kxe6 59.Kxc5 [59.a5 Bd8+ 60.Kb5 Kd6 61.a6 Kc7 62.Kxc5 Kb8=] 59...Kd7=) 56...Be7+ 57.Kb5 (57.Kd5 Kf6 58.c5 Bd8! 59.c6 [59.Kc6 Be7=] 59...Bc7=) 57...Kf6 58.Kxa5
In this amazing position, White has four pawns for the piece, but it is still a draw: 58...Kxf5 59.Kb6 Kxe6 60.c5 (60.a5 Bd8+ 61.Kb5 Kd7=) 60...Kd7=.
These lines were, of course, very difficult to calculate in a real game. After Koneru's move, Hou is winning.
45.Bxc5 Bd8 46.Bf2 Be7 47.c5! Bf8+ 48.Kg5 Be7+ 49.Kg4 Ke8 50.Be1 Bxc5 51.Bxa5 Be7
Here Hou missed the clearest win.
52.Kf3?! (52.Bc3 Kd7 53.h4 Ke8 54.h5 gxh5+ 55.Kxh5 Kf7 56.a5 Bc5 57.a6 Be3 58.Kg4 Kg6 59.Kf3 Bb6 60.Ke4 Kf7 61.Bd4! c5 62.Bf2 Kg6 63.Be3 Kf7 64.f5! exf5+ 65.Kxf5 and, despite the limited material and having the "wrong" rook's pawn, White is winning. For example, 65...Ke7 66.e6 Kd6 67.Kf6 Bd8+ 68.Kf7 Kc6 69.a7 Kb7 70.Bxc5 Bh4 71.Bd4 Bd8 72.Bf6+-) This again would have been extremely difficult to calculate, and you can understand Hou's decision to leave more pawns on the board.
52...Kd7 53.Ke4 c5 54.Kd3 Kc6 55.Kc4 Bh4 56.Bd2 Bf2 57.h3 Bg1 58.Bc1 Bf2 59.Bd2 Bg1
Position after 69...Bg1
60.Kd3?! Here the breakthrough 60.f5! works: 60...gxf5 (60...exf5 61.e6 Bh2 62.a5 Bd6 63.a6 Kb6 64.Be3 +-) 61.h4 Bh2 (60...Bd4 61.Bf4 +-) 62.h5! Bxe5 63.h6 Bf6 64.a5 e5 65.Be3 f4 66.Bxc5 e4 67.h7 e3 68.a6 e2 69.Bf2 Bg7 70.Kd3 f3 71.Ke4 +-
60...Bf2 61.Be3 Be1 62.Kc4 Bb4 63.Bf2 Kb6 64.Be3 Kc6
As is common in this type of ending, Hou is maneuvering with her bishop to try to put Koneru into zugzwang.
65.Bg1 Kb6 66.Bf2 Kc6 67.Bh4 Bd2 68.Bg5 Be1 69.Be7
69...Bf2?! After 69...Bb4, Hou still had to find a clever triangulation to win: 70.Bf8 Kb6 (70...Ba3 71.a5 Bc1 72.Bxc5 Bxf4 73.Bd4 Bg5 74.a6 Bd8 75.a7 Kb7 76.Kb5 Bh4 77.a8=Q+ Kxa8 78.Kc6+-) 71.Bd6 Kc6 72.Be7! Kb6 73.a5+! Kxa5 (Black would like to keep her king closer to the center, but the point of White's maneuvering is that 73...Bxa5 allows 74.Bd8+) 74.Bxc5 Bd2 75.Bd4 Bxf4 76.Kc5 +-. Now the win is more straightforward.
70.a5 Be3 71.Bg5 Bf2 72.h4 Bg3 73.a6 Bf2 74.h5! A nice breakthrough. 74...gxh5 75.f5 exf5 76.e6 Bg3 77.e7 Kd7 78.a7 1-0
Hou held the draw with black in the second game, thereby advancing to the final.