In that case: she knew when she awakened next morning that it should have killed him. If she had known that the night before, then after disabling Draco with the charm, she should alerted a teacher, or maybe woken him up and stunned him the usual way. If she didn’t do any of that, she was knowingly leaving him to die.
What about the possibility that Draco attacked Hermione with sufficient force that the blood-cooling spell was plausibly self-defense?
A “blood-cooling charm” doesn’t sound like it would have had enough stopping power to be effective in self-defense.
In that case: she knew when she awakened next morning that it should have killed him. If she had known that the night before, then after disabling Draco with the charm, she should alerted a teacher, or maybe woken him up and stunned him the usual way. If she didn’t do any of that, she was knowingly leaving him to die.