see the golden designs on her clothing look like cheap ironed on patches as they fray out into the air on the edges.

They are in fact very expensive, sew-on patches. They’re embroidered by hand on separate fabric, and then sewn on the dress. It’s a hell of a lot of work. The gold work here looks like a specially woven brocade (woven with actual precious metals)

The edges are finished with cording (stitching over the edge) to prevent the fabric from fraying. They would eventually wear out though, but since each piece is so expensive, they’d wear them for a long time. And since these pieces were often made with literal gold and silver, they’d be removed from clothing, applied to new clothes and we’re often heirlooms.

almost looks as though the white layer is a separate garment entirely

Indeed, it looks entirely like that! Beautiful.

Appliqué technique, it’s still used today.

The best source I could find: https://renaissancetailor.com/demos_appart.htm Unfortunately the site has badly implemented copy protection, or I’d have copied a short explanation.

Good at dresses, bad at faces