"However, if both sides are committed to continuing the fight, they may each give you a Plot Point to continue despite your Interference. Both sides must buy in, at which point all three of you make one roll each. The two combatants should describe what they’re doing to continue the fight before you describe your character getting in the way, or cowering, or what-have-you.
Compare the results of the two players in the Contest; whoever has the highest result inflicts Stress on the other side. Neither side gets an opportunity to Give In; your Interference has made the Contest about hurting the other side. Additionally, if either of their results is higher than your result, they inflict Stress on you. This may mean you take Stress from both sides!"
Can someone interfere if the contest has already been resolved? Is it then just a new contest? Aina agreed to leave with Mopsa and calm down. Now Walter is starting a new contest to get information?