Oh, for heaven's sake. 'Henpecked,' 'severe blow to B's ego,' nonsense. We don't have any idea whether B even likes to eat out or not. All that is pure projection. Let me get out my violin.
'Green eggs and ham' sounded awful to me, so if I were projecting from a different angle, I could read into it that A might be an enthusiastic cook of unusual dishes. If so, B might be aware that A feels better if he sounds enthusiastic about home cooking, whether he really in the bottom of his heart likes green eggs quite as much as he lets on or not.
But it's equally possible that A, with tomorrow set to be a long day at work, doesn't really want to cook at all, in which case it does seem rather odd of B to first remind her that they were going out, but then say he doesn't really want to go out. In that case my projection might just be that B, perhaps a less decisive person, has realized as he mulls it over that he doesn't really want to go out after all -- maybe he'd rather not spend the money, or put on nicer clothes, or is just tired as well and would rather eat in if it was totally up to him. That could all be the case even if he's a nice and flexible person and doesn't want A necessarily to have to cook, and is genuinely willing to do what she would prefer. Though that can lead to frustration if what A would really prefer is for B simply to express his opinion more decisively for a change. It can also lead to frustration if B's opinion (as A can predict) is always that he prefers to go out for something unhealthy and fattening, like fish and chips and beer, when A would really prefer a nice restaurant.
But not knowing A and B any more than we do from the forum, we don't know which one more often suppresses his/her own interests and is more willing to adapt to the other's preference, or which one more often manipulates the other one into doing more work or making more decisions. It could be either one of them, or it could vary depending on the issue. Or in fact (since they seem generally happy and have been together a while) they could be one of the 2% of nondysfunctional couples who often agree and are pretty good at just sharing and/or taking turns. (For L.G.'s sake we certainly hope this is the case. (-: )
Purely from knowing that A is female and B is male, my hunch based on observation is that the one least likely outcome is for B to volunteer to go to the grocery on the way home and cook something nice from scratch, including vegetables, since A has a long day at work. That's the feminist angle.
But that's a libel on the enlightened B's in the world who really like to cook (sebastianW, perhaps, among us here), or are genuinely committed to sharing all housework 50-50, and are perfectly willing to step up to the plate and fix something fast, healthy, tasty, and home-cooked for supper, even on a weeknight after work. I would certainly like to hope that there are more of them out there than there used to be. (-: