Alright. So,
@Arkeus suggested that Chu Song is here to delay us because of Ji Rong. That is, she's not fond of Cai because Cai (rather impulsively apparently) sent her goon squad to demand Ji Rong's return to her from Chu Song. This is a misplay both because of what Fu Xiang already told us about Chu Song but also because she underestimated the strength of the bond between Chu Song and Ji Rong such that Chu Song was willing to fight Cai if Cai's' minions did not back down.
@Arkeus also suggested that she's here to propose an alternative alliance between Meizhen and Ling Qi with her vs. Sun Liling (and also that she's interested in talented commoners like Ling Qi).
But one way talk could work out is that I think we can convince Chu Song that Cai Renxiang would be better for her and Ji Rong with Ling Qi's help. First, as
@yrsillar pointed out, Sun Liling isn't really that good for Ji Rong either considering he was used as a pawn in the last fight and given that Chu Song isn't too fond of Sun Liling either (bloody princess), it's probably something she's figured out as well.
We have enough connections that I think we can sell Cai Renxiang on the politics of this -
1. Ji Rong has already served his time for the original offense - and a month of enforced inactivity is sort of overkill as a punishment
2. His participation in the Pavilion Fight was as a "disposable berserker" to be used and discarded by Sun Liling (i.e. Sun Liling led him astray)
3. With Chu Song there to guide him as his big sister, this won't be an issue in the future
TBH, Chu Song is strong enough and with enough connections that Cai Renxiang can see the benefits of 'forgiving' Ji Rong as a favor to Chu Song (and to put Chu Song on the council) and this would be a way to draw in and coopt a major power faction in the Sect. This puts her faction in a much stronger position, and she's already been willing to make allowances for council members (a la Ling Qi and Su Ling and Li Suyin).
On another note, we can easily talk around the terms of Chu Song's favor
so long as Chu Song is willing to work with Ling Qi in finding those technicalities. For ex., Ling Qi might only be barred from interfering in the Sun Liling vs. Cai Renxiang 1v1 duel. If Chu Song is willing, Ling Qi should be able to interfere in any other fights that may or may not be ongoing (i.e. Meizhen vs. ?, Gu Xiulan vs. ?, etc.) and free them up to help Cai Renxiang in turn.