Board Thread:Questions and Answers/@comment-24098614-20161028233850/@comment-26527700-20170127212518

Well she did implant a message into his brain in the Railgun manga. However she indicated that she needed to get the angle right, demonstrating that doing so likely requires precision control of her power. In contrast, the telepath in volume 6 of the LN (at the underground shopping mall) couldn't communicate with Touma, likely because her lack of precision results in Touma's hand cancelling it.