It looked to me like Cally was basically in shock when she went in to the launch tube, but that Tory had actually talked her down…right before Tory attacked her. That deception is what makes her evil.
When it comes right down to it, I don’t think Cally would have actually killed her son. As she told Tory she was doing it to protect him from the Cylons. Once she started to come out of her shock, she expressed regret for what she had done involving her son and at that point, I think she wasn’t a threat.
What really cheeses me off is that from a technical standpoint, this episode was AWESOME. The scene with Cally in the maintenance spaces of the ship and then the scene in her quarters with the Chief were just frakking amazing.
But to flat out murder my favorite character…I’m not down with that.