I learned that term in a cover lesson I was teaching once; it means the audience are in on something that the characters aren't.
Both end with the characters very happy with their lot, but as an audience we're aware that they maybe shouldn't be. I think.
I mean, I can't tell if working girl is a knowing ending. The protag is totally happy with her new situation; and maybe it was, at the time and place of release, a catch. But the final camera shot, zooming out of her small (but private) office, seemingly only a floor up from her old open plan office, just underlines how worthless it is, how unremarkable the achievement, how dystopian the world of skyscraper business deals with money and rights changing hands for completely impenetrable reasons and effects. The fact that she simply appears to be in the same building as before (maybe not, but then the ambiguity is telling isn't it?) just adds to the apparent lack of progression.
For its realism, WG should be applauded; the protag doesn't get given an office of surreal proportions on the top floor of a tower. But the realism is pathetically contrasted with the cinematic nature of the ending, and the gulf between her glee and the utterly pedestrian reward creates that ironic sense.
I can't tell if it's a deliberately mismatched ending intended to give this sense, if it's just time that's given a sad view of what was considered aspirational in the 80s, or if it's just me that has seen something that's not there. But it really reminded me of Brazil, from the typing pool, through the pointless obsessions of the distracted classes, to the utterly depressing realisation at the end. They'd make a good double bill.