What if Andrestia was initially taken in by The High Riders, but over time, came to sympathize with The Gladiators. She could start out being taken into the higher society, and cared for in a similar vein as Perturabo was with his adoptive father. But when seeing the beings on The Red Sands being forced to battle each other to the death, her nature swells up and has her try and end this tyranny. Could lead to an initial rebellion to free those in the pits, which ends up failing because it was mostly an act of passion and ill thought out. She gets ousted from the High Riders for trying to ruin their games, and is told that if she loves her gladiators so much, she can join them.
I kinda like the idea of Andrestia choosing her name, as the aspect of Revenge or Retribution, as a means to declare herself in getting the justice deserved for The Gladiators and those others under the High Rider's rule.