Why is she splitting a Peach?? I have no clue. Perhaps it means to say that she doesn't need peaches no more since she can sleep around with men to heal herself?
Who is she:
Best remembered as the martial-arts loving wife of Liu Bei 刘备, Sun Shang Xiang is the younger sister of Sun Quan 孙权. Since young she loved martial arts and even has all her maids carry swords wherever they go. She was offered to Liu Bei as his third wife by Sun Quan and on the surface it appeared to be a strengthening of the Sun Wu 孙吴 and Shu Han 蜀汉 alliance. The reality, however, was the marriage offer was a trap plotted out by Zhou Yu 周瑜 to lure Liu Bei into the Kingdom of Sun Wu and hold him ransom in return for Jing Zhou 荆州. Yet in one of the most lauded schemes of Zhu Ge Liang 诸葛亮, Liu Bei not only successfully marries Sun Shang Xiang but also escapes back to Shu Han with her. In his rage, Zhou Yu orders his troops to kill Liu Bei even if it means having to kill Sun Shang Xiang, but the chase met with an ambush from Zhu Ge Liang and Zhou Yu ends up losing both Sun Shang Xiang and thousands of troops.
Thus the famous saying: "To lose a lady in addition to losing numerous troops 赔了夫人又折兵"
Character ability 1: "Marriage 结姻 (jié yīn)"
During the action phase, Sun Shang Xiang can choose to discard 2 on-hand cards and pick any male character (not player!) that is not at full-health. By doing so, both the male character and herself will recover 1 unit of health each. Limited to only 1 use per turn.
Character ability 2: "Warrior Lady 枭姬 (xiāo jī)"
Whenever any equipped card is removed from her equipped items area, Sun Shang Xiang can immediately draw 2 cards from the deck. Note that 2 cards can be drawn for each equipped card that is removed. This applies also to changing the equipped item (ie: replacing one weapon with another weapon).
Ability's relation to story:
"Marriage" is, of course, referring to her marriage with Liu Bei. The inside joke is this ability is commonly scandalized into "Intercourse" and since it can be used with ANY male character, she has become a slut of sorts. It does not help that her character art gave her a pair of huge jugs spilling out of her top. "Warrior lady" refers to her love for martial arts, but little connection is made with the mechanics of the ability with the storyline.
Additional info based on story:
1. Most famous achievement - Her "escape" back to Sun Wu. In another ploy, Sun Shang Xiang was tricked into believing her aging mother was very ill. At the time, Liu Bei was away conquering the Western regions near Cheng Du 成都. She decided to leave for Sun Wu and bring with her Liu Bei's son, Liu Shan 刘禅. This threw up a huge fracas as Zhao Yun 赵云 and Zhang Fei 张飞 braved enemy arrows to convince her to return. Alas, Sun Shang Xiang would not listen, but relented in returning Liu Shan. Upon finding out it was a ploy, Sun Shang Xiang was extremely upset. She never got to see Liu Bei again.
2. Cause of death - Legend has it that Sun Shang Xiang committed suicide after hearing about Liu Bei's death. She threw herself into a river and drowned herself.