The main symptom of levodopa is dyskinesia. What you would see at the very least is a slight swaying or rippling in her body as she stood by herself away from the lectern. That didn't happen in the last debate, so she was not on levodopa, at least not a non-trivial dose. With Parkinsons there is no happy medium between lack of dopamine and too much dopamine. It is always one or the other. The stress of the debate would have caused tremors, or with levodopa to cover the tremors, dyskinesia. She had neither.
As I said above I would not rule out any sort of neurological damage considering her history of blacking out (often as Bill Clinton accidentally admitted) and the vision problem. And those are just the problems we have heard about or can see. But my experience with Parkinsons and levodopa is that she doesn't have it and is not on that medication.