Location: Qingmu Sect
Prerequisite: Complete Qingmu Sect History
Petitioner: Sima Ling
Petitioner: Sima Ling
Reward: Pink Plum, Cinnabar Plum, Longyou Plum, Martial Arts Thoughts
To trigger this side quest you first need to complete Qingmu Sect History, which itself requires that you complete all three of Shangguan Hong's side quests. Speak to Sima Ling in her usual spot in Qingmu Sect - in the east, with most of the other members of the sect - to begin the quest.
It appears that Ling has received her wish: Permission to leave Qingmu Sect and travel the world. First, though, she must prove her strength in a battle with other members of the sect. Yi and Ling will need to face them together to earn Ling's freedom. You can trigger the fight by heading to the west end of Qingmu Sect. Here you'll receive Mineral Drugs Powder and Three-Times Refined Spirit Pills. Speak to Chuchu, the lead disciple, to begin.
Chuchu, Ruirui, and Shishi
This is a relatively simple battle. Your true opponent is Chuchu, who wields a sword and primarily hits in straight lines. The one exception is her Thunderbolt Swordplay attack, an AOE move that spreads outward in a diamond shape. Ruirui and Shishi are both unarmed fighters, and use simple punches.
Unless you did nothing to power up Ling in the previous quest this battle shouldn't take too long. Use Lightness and wait for the three warriors to move towards you, then surround Chuchu and beat her down. AOE attacks will allow you to hit the other two in the process. This fight is about as difficult as a normal field fight, and won't take long.
Winning this battle will end the quest, raising your Affinity with Ling in the process. Head back to Ling's normal spot and she'll be waiting there - and mention her wish to visit Jinli Village. At this point you can Invite Ling into the party, assuming your Affinity with her is 60 or higher.