Peer ? Tell her to STFU. Diplomatically of course.
I’m always a tad surprised when women wear sandals or flip flops to work in places where folk would look askance if a guy did the same. .
There was a controversy in 2005 when a women’s college sports team was invited to a ceremony inside the White House and half of them wore flip-flops. I think that was around the height of the flip-flop craze and most of the students grew up thinking flip-flops were formal wear.
The article linked above also has this interesting tidbit:
How many men would be willing to shave their legs everyday?
A peer dressed you down? For wearing jeans and a nice shirt?
I’m glad I don’t have to put up with dress code bullshit.
If a man wants to show in a kilt I’d be very on board with that… 
I would think capri pants are almost never business casual. Especially anything that looks like beachwear.
I can think of some capri business casual looks I’ve seen - wider legs (almost "gaucho pants) in a crepe type fabric with a blouse.
Of course, there is no way to tell her this…its a roll your eyes situation.
I drove through Nevada on I-80 once, stopping at various of those little desert towns along the way. One had a little museum. In it, there was a full tuxedo made of denim, custom-made for some notable.
Maybe something like the pictures here, although I remember it styled more like a real tuxedo and less like a zoot-suit. (This was some years ago, so I don’t remember a whole lot of detail.)
Red carpet ready:
My brother got married in a denim tux. Enormous lapels and huge bell bottoms. It was 1975 in California so not too out there.