This is going to sound crazy...
But you would be better off if your t was a contract killer and kidnapped your real mother and tied her up in an abandoned warehouse...then brought you there to to make the decision of mercy or justice.
Once the decision is made...no more of this good enough or not good enough crap...
Once your decision is made which I'm guessing she'll be shown mercy, then your mother comes face to face with the idea that YOU rescued HER from YOU and the effect she had on you.