M.R.
She's honestly got a very healthy view of it right now.
As a child, it's only natural that she gets a little scared over events such as 9/11 and her father joining a more hazardous line of work. But it's the rationalizing it to herself that will take time. And so far, she sounds like she's doing a good job of it.
I have to commend you for taking on such a difficult conversation at a young age. And from her response, you did it just fine.
Have her talk to her father now to finish rationalizing it in her mind and she should be at ease in a few days.