Going with Brandish here, since this isn't a battle royal, Minerva would have to fight one of them, and I don't see her defeating an injured Brandish or Kyria.
I see it going as Minerva hides at the beginning of the battle allowing Brandish and Kyria to fight, using the same tactic as she did against Erza and Kagura in GMG, in which I think Brandish could take Kyria mid diff which leaves Minerva vs injured Brandish, in that case I can see Brandish low-mid diffing at most.
But, yet again I can see Kyria winning via hax, but same could be said for Randi. So, for now unless someone can change my mind. I'm going with Randi.
But, if Minerva decides to join the fight at first then she gets take out by Brandish or Kyria without much effort, still leaving those two to fight.