That presupposes that she would have been spared if she said "no," and those two scumbags probably would've shot her anyway because Cassie was well-adjusted, well-liked, and well-respected in the school--in other words, she was everything that they weren't.
No, it does not.
Cassie Bernall was picked out because she was reading her Bible in that library. Her killer(s) already knew the answer to the question. She chose to be a witness for Christ and answered truthfully, "Yes." It was the last act of a faithful and obedient servant of God.
I hope, when all other hope is gone, that I too will respond accordingly. In the meantime, I fight the good fight on several fronts. That fight at present consists of words. But there may come a time when persecution becomes very real. It won't be labeled as such. There will always be some pretense: racism, intolerance, child abuse, terrorism, to name a few. No Christian should "live by the sword", but each should know how and when to use one.
And you've presupposed that she would have been shot anyway.