Ok so my view on her outfit.
It was appropriate for the occasion and it was ok. But she could have styled it much better.
M has a tricky body shape in that (though slim) she has a square torso with an ill defined waist. I say this without meaning to be derogatory as my frame is very similar 😂.
It can be an absolute bugger of a shape to dress. If you get clothes that fit your shoulders/hips they are invariably too tight at the waist or if you fit to your waist you end up with clothes that just look oversized around your hips/shoulders and make you look much bigger than you are.
So you have to dress/style strategically. In terms of jackets, cropped jackets that end at the smallest part of the waist are a good option.
Another if you want to wear longer jackets is to fit to your shoulders and wear them unbuttoned (so they don’t pull at the waist as we see happening in the pictures of M).
The other option is to lean into the oversized “boyfriend” baggy blazer look where clothing deliberately isn’t cut to accommodate a waistline (M seems to do this quite a bit) but it often risks you looking totally shapeless and isn’t a very “polished” look for a formal occasion.
Of course you could get items tailored but that’s going to cost (but imho I’d argue if you are going to spend over £3k on a designer jacket then there’s no point in doing so unless it fits you properly or are prepared to wear in a flattering way).
IMHO she’d have looked great in the jacket and trousers if she’d paired them with a contrasting cream/ivory (or other colour) fitted shirt, a good belt to define her waist and left the button on the jacket open (the contrast shirt would have also addressed the issue of the different shades of black between the jacket and her top).
So no, imho it wasn’t so much an outfit catastrophe but rather a missed opportunity that could have been styled a lot better.