Sometimes things happen—work, schedules, life—but getting in-touch to reschedule or cancel shows that you value someone else's time. Too often, however, first dates are a no-call/no-show... and unless there in an emergency there's really no reason for it. It's just common courtesy.
What she wants: A simple phone call. Not a last-minute text message canceling the date... a phone call. It shows integrity and that she is worth more than a technology-based blow-off.