But she's been human this whole time, Aku only activated her other half. Which means, if her other half was removed, she would still be a normal human.>b-b-but science...
Too bad bitch, magic demon jizz, science invalidated. Its a Aku suit.
Now I can say, it would be unrealistic if she gains the power to just suppress her Aku side, but its not unrealistic to believe the Aku essence inside her can be removed. Aku essence follows well established rules, like with the Aku Infection. She definitely can't fight back the Aku side on her own, but if Jack does some power of love bullshit, she can likely push it off of her body with sheer willpower due to cliches.
Look, I am sorry ok, I am sorry you hate Ashi and want her to die, but you shouldn't be acting like her death is already confirmed in a series as cliche as samurai jack. Especially since Ashi is special, because "this has never happened before" from Jack. People are pissed he didn't kill her when she asked for it, but then she would just be another innocent killed by Aku like all the others, and he doesn't feel that way, he feels stronger for Ashi then anyone else. Honestly, the best you can hope for is Ashi impales herself on Jack's sword killing herself somehow, because Jack's not going to do it himself.