'Virtue signalling competitive non-eating' is a brilliant descriptor, and it's beyond tedious.
...Quite frankly, OP, I find the idea of a group of women ordering food - the production of which consumed fossil fuels, land, water etc. - only for everyone to watch it until it was taken away untouched in some bizarre ritual of self- and mutual-abnegation and one-upmanship to be utterly fucking ridiculous. I mean, embarrassingly so.
The described vapid, affected hysteria at the notion of chicken pie (gasp!) is the icing on the (uneaten) cake - I don't know how you tolerate it.
That said, I often order salads or other vegetable preparations. But I don't say, "I'll just have the salad", I'll just say, "I'll have the salad". I'm a vegetarian, and although I do aim to eat largely for nutrition instead of entertainment, I enjoy salads and vegetables and whatnot.
Plus if it's an on-the-fly plan, quite a few of the quick table/bistro places pretty much have salad, chips or roast vegetables cross-contaminated with roast meat (nope!) as the sole 'vegetarian' options. So sometimes it just works out that way.
I'd be horrified though if I discovered that a lunch companion felt shamed out of eating something she wanted by my choices.
If someone ordered a cheesecake and it looked really well-made, I'd order one myself and be aaaallllll up in it.
I do know people who constantly titter on about how 'naughty' they're being, or how 'guilty' they feel, or how 'bad' something is.
I'm just sitting there thinking, "Bitch, it's a Tim Tam, not fucking crack cocaine".
I've had more than one adult do this in front of my little niece or younger sister, and I give them the verbal smackdown right quick. I'll be damned if I'll allow anyone to infect my girls with that toxic nonsense.
Which is all to say that I'd struggle to enjoy the company of a group of women who spent the meal self-consciously policing my - and their - intake in service to absurd patriarchal tropes of femininity... We all know the song (or at least a verse or two):
Valuable woman = woman who is desirable to the majority of teh menz and makes them feel big and strong and manly-like
Desirable woman = super 'feminine'
Super feminine = among other things, dainty/delicate waif
(Four years ago, my partner's mother, who is in her mid-fifties, said to me, quite seriously, that she would happily take ten years off her life in exchange for the ability to eat whatever she wanted from now on without gaining weight. Four years and I'm still grappling with just how bleak that is.)