I'm way, waaay older than Nozomi, & as a widower nearing the five year mark after my wife's passing, I can say that Ritsuko is talking out of her ass. I didn't experience the deep, bitter, 'screw up your mind' kind of grief until almost a year had passed, so Nozomi is still in the shock phase of grieving. Since Shino also lost Taichi, those two would naturally mutually support each other. At this point, I don't see it as unhealthy. I was kind of grateful to be able to run on autopilot for a couple of years, using my job & books as a way to fill my days. Of course, it could eventually degenerate into unhealthy dependency, but with Shino starting to change her life (ah, the resiliency of youth), I think Nozomi will finally start to build a new life. But a bumpy road still awaits both of them, regarding to dealing with their loss & lack of vision for the future.