May I politely suggest that a call to the flight deck WHILST ON THE ACTIVE RUNWAY directly contravenes Qantas FAM rules. This is called the "No Contact" period. Flight Attendants ARE aware that they arent to call the flight deck under ANY circumstances, let alone for an issue like this, that should have been sorted at the gate.
Suggesting the Captain should be shot is extremely poor form. Gomi? As you state, there are rules for a reason. But which are more important? Exceeding duty limitations, or in an extreme case, having 400 people die because the flight crew were distracted on an active runway dealing with whining cabin crew who decided that their query during a NO CONTACT period was more important!!
Now I have no idea what went on here, but from what has been stated thus far, the cabin crew member who called the flight deck at this time SHOULD at the very least be stood down pending an investigation.