I had a difficult time understanding Kate. I think I would have understood her conflict better if I HAD NOT read The Expats after finishing this novel. (Funny, considering I might have enjoyed The Paris Diversion more if I had actually read that one first.)
Kate did not have a job in the first book in the series- -she gave it up to move with her family to Luxembourg. And she complained incessantly about all the "boring" things she had to do as a stay at home mom. She even knew the exact number of times she had cleaned a bathroom sink! She has an opportunity that she created for herself in her new position. She still complains! What is different about Kate and many women who must juggle work and home is that Kate HAD A CHOICE. Many women do not.
I also believe that Kate's dominance created some of her issues. She was not willing (or comfortable) giving Dexter more responsibilities. As a day trader, working from home, Dexter really had the time and flexibility to help Kate more than he did. I get the impression that her need to be in control prevented him from doing more. Kate seemed to treat him more as a third child than an equal partner.