Shi Yin was sick and delusional. Lee and Xiao Yun were having a duel. She arrived just in time to see Lee accidentally wounding Xiao Yun. In her shocked state, she picked up a sword near by and stabbed Lee. She lost her mind after that and reverted back to when she was 16.
The first two captions are from Legend of Dagger Lee, when Shi Yin was marrying his "brother".
The next two captions are from Fei Dao Won Ching - Lee and Shi Yin are together again after she recovered her memory.
Final duel with his new brother. The brother turned out to be a prince from another country. He wanted to invade Lee’s country. Neither wanted to duel but they are destined to be on opposite sides.
First two captions show the end of the duel. The brother lost.
The final duel had taken its toll on Lee, both physically and emotionally. He's very tired and throwing up blood. He lies down to rest. The last scene is of him "sleeping" on Shi Yin's lap. They never said he died.