Sewing fine fabric

I wouldn't risk this with something belonging to someone else tbh.
I know the sort of heavy beading you describe and think it will tear. Maybe less likely if some tough modern synthetic I suppose but I'd be very wary.
What fabric is it?
Mine is silk and very gauzy.

Not sure if it isn't ruch !?
Or is that the Anwrican spelling ?

I'd be careful with this .
I once stitched a heavy beaded collar to a fine net dress and the net tore .
Both were antique from the 1920's and I didn't raise how fragile the material had become .

I'd stitch a satin ribbon to the collar and make a bow .

If you rouch up the ribbon it won't look out of place .
You could even pin a diamanté brooch in the centre of the bow and it would look a deliberate part of the design .

Thank you all for your suggestions and good wishes. I hadn’t thought about it pulling the dress, which I think it may do as it’s heavy. Will try some small safety pins and wear the dress at home for a bit. If that fails will have to replace it with a boa.

Sew some thin tape along the hem/edge to strengthen it, prevent tearing and stretching. This should then be easier to attach to the dress. If the tape would be too visible, perhaps just boldly edge it with a matching braid to give yourself something to stitch into.

In fact, with a braid or ribbon edging you could use tiny safety pins to fix it in place.

You could try a couple of very small fine safety pins on the inside of the dress just catching the beaded net on the outside. You can get these in different colours so they wouldn’t show- attach to the dress seams and the shoulder seams of the collar. In addition you could hand stitch some fine stitches to firmly anchor the collar in place.

Absolutely no idea....but it sounds like a fun evening...enjoy

Stitch it near a seam that can take the weight in a few places. Have a lovely time I adore 1920s music dress and style.

You should be able to stitch the net without damage but make sure to use a very sharp, fine needle. I hope you have a lovely time in any event

If it is heavy, it may just pull the dress with it when it moves, and make things worse. Try it and see but try it before the event.

I would hand sew a couple of stitches at the back of the next to keep it from sliding off, and remove then after the evening.