Maybe she just left because she'll find it harder to leave if she told Tench she's leaving? I remember when I first watched I really hated it because she left with their son and he had no idea. Now that we're talking about it, I do understand the wife because she has no idea what was going on. Tench can't really talk about work with her and I'd argue that she should be more understanding but then Tench was always not around too and he should also spend more time with his family especially that his son is going through some stuff.