The terms of the challenge state that she can't tell anyone about it before or after the duel or it goes to the Wizangamot. So, no, presumably she can't tell Harry about it.

Heck, she might have severely injured Draco by accident, rendered basic medical care, and then just left, because she can't tell anyone. If someone found Draco unconscious and half-dead later, and they figured out Hermione did it and left him, that would look like attempted murder.