[Miyako's got a lot of reasons to distrust most people, and she herself has a few trust issues stemming from the fact that she herself has not always been trustworthy. She isn't dismissing the possibility that this stranger will be helpful, but the consequences of him being an enemy would be so much worse. Yet there's no reason to make him hostile by continuing to reject him. She sighs, and opts for blunt honesty.]

If you wish to come along, then I doubt there would be much I could do to stop you without causing harm to myself. Frankly, having seen the end of your battle against these...patients, I am loathe to travel with someone whom I do not know the intent of and who could also overpower me.

Yet if you have no intention to do me harm, traveling with you would prove very advantageous. I admit to being torn as to what would be the best course of action.

[...which is kind of a non-answer, but she's hoping to see his reaction to help her better gauge him as a whole.]