In the portrait, she is wearing a smock, which is decorated at the collar and gathered sleeve cuffs with whitework, in the form of a series of ornate diamonds with rosettes placed inside, and groups of four small diamonds in between. It is possible that it was worked in a double running stitch (Holbein stitch). This is a style of embroidery that was very popular in England and parts of Europe in the sixteenth century.
The gown she is wearing is decorated with bands all worked with the same design, but it is not clear whether these are woven or embroidered forms.
See also Hans Ewouts's portraits of Bess of Hardwick and Lady Dacre.
National Portrait Gallery online catalogue (retrieved 29 June 2016).
GVE
Chart of the whitework pattern on Catherine Parr's collar. Drawing by the author.