this was either done by hand or you can use a cording type foot and buy the beading already strung or you can string it yourself.
most couture wedding dresses are by hand and the "off the rack" are typically done by machine.
you don't have to use beads if you don't want any trim that she likes can be used.
a fabric store that carries fashion fabric will have what you need. if you happen to live near NYC you can pick all this stuff up in the garment district.
you could also check online from bridal trims.