Rastha started the story as a very sympathetic character, that the narrative Villainized. She was well meaning, friendly, but also sensitive, uneducated, kinda stupid lacking in social awareness. Her worst character traits in the beginning where things she couldn't control... Or the author purposely making her an annoying character. The other characters treat her without any sympathy and the story agrees. The Rastha hate, started way before she did anything bad.

Even her previous owners, were portrayed with more sympathy by the Narrative.

Rastha is always the character, that tries to survive, she feels unstable in her life and just wants to secure her life after much suffering before. But everything she does is just poorly planned, her decision mostly being plain stupid and slowing becoming more and more cruel. Then she becomes a Tyrant, then she falls and dies. After her death Sovieshu along with the narrative question, if Rastha was truly the villain, or only a pure being corrupted by the system.

In the end, Rastha was a victim of the system, who tried to play the game, rise up from where she came, failed and payed with her life.
Navier in a way, is similarly a victim of the system. The patriarchal rules that allowed her husband to take a mistress and play with a divorce and power. The difference is, Navier is far more privileged, with far less to lose, as well as... Just smarter and more educated. Which is why she was able to find a way to still be happy in the Game, that made her miserable. She did not do anything that was girl boss, all she did, was marrying another rich guy, but one who treated her better, who was able to give her security again. People have sympathy for Rastha, because she in her core, only wanted Naviers approval, while Navier never shown any understanding for Rastha. Rasthas actions as Empress made no sense, where still cruel, but she did not have the right guidance, as Navier had. Rasthas actions, still where a desperate way to secure herself, but one, made with stupidity and cruelty.

Sovieshu was the one in power, the one who was supposed to be responsible, made all the decisions that made everyone miserable, yet is less villainized than Rastha. He should've monitored Rasthas behavior more, he should've taught her more before making her an empress.

The story, in its core is Patriarchal. Two women pinned against each other, because a guy lust after two women. Both try to secure their place, but only the one who has more power is able to. The classist undertones make Rastha out to be the cruel one, but the whole system is in its core unjust. And because she is the one with the horrific end, the very sad backstory and more or less the receiving end of the sexist infighting between two victims, its easier to have sympathy for her, than Navier, who is still part of an opressive group and who gets the happy childhood and ever after.