In the premise of the scenario, she was alone. It is unlikely, but that is how it is presented. If the woman was cornering you in an alley on her own, then she was out for blood or some other off the record action.
I think the point of this question is about the fight or flight scenario. It's nearly impossible to predict how your body would react to the situation, but I don't think you are going to be thinking about the consequences when someone comes at you. When I think of being afraid, I think of an adrenaline rush. I'm not scared of the prospect of being harassed or stalked. Assuming that the woman approached me in the alley and directly accused me of kidnapping her child, she has doubts. She has no reason to accuse me. If she is right, then I know what I did and she doesn't need to tell me, let alone in an alleyway. She would be putting herself in danger by doing so.
The thing that scares me the most is that she is coming at me alone in an alleyway expressing her accusations off the record. She is already being irrational. She is unpredictable. Her motives are unclear. And should she try to attack me, she has no reason to give up until I am dead.