I just completed the Retribution quest by killing one of the traders, letting one escape. After completing the quest by speaking with Burne I checked the Co8 companion list to find out Pishella is recruitable as a companion, yet no matter how much I talked to her the recruit option wasn't available. Luckily I always have a dozen or so saves I cycle every time, and I could test the option does appear normally until you kill the trader/s. The last save where I could recruit her was the one in front of the trader, pre-buffing, just before confronting them with the assassin's letter and starting the fight. As soon as the battle is over, even without reporting to Burne, she won't be recruitable anymore. Is it safe to just load that save, recruit her, and then kill the traders? What I'm afraid of is that killing them will change whatever flag that doesn't make her recruitable again, and that in the future, if I ever decide to temporarily dismiss her, I won't be able to get her in my party again.