There is not much other traffic in immigration/customs at that time of the morning - when I've been on the morning arrival from NRT, I've never had any problems getting out of immigration/bag reclaim/clearing customs quickly.

Tell her that when she comes out of the immigration hall to go upstairs and follow the signs for the Grand Hyatt. There is a security line there that is virtually unused - 5 minutes wait at the busiest times I've seen it (and its close to where immigration will spit her out). From there is about six to seven minutes on the interterminal train to A.

I'd see no problem making this. The last time I came in on the morning arrival, I was at my office (five minutes drive from Terminal D) less than 30 minutes after landing and that was WITH checked bags.