Hard to believe this was a slip-up on her part. Everything that Hillary does is scripted. Again, I think she may be baiting Trump into some sort of response. I am not sure he was made aware of this information during his security briefing once he won the GOP nomination. If so, he needs to tread very carefully here.
She could be trying to entrap him to making some comment that would reveal a true military secret and maybe then have him arrested.
I think you are right about it being a baited trap. talking about are emergency response time with nuclear weapons just seems stupid to do. as a voter it is not anything I need t know and is detrimental to be known by are enemies in a crises.