However having put all this work in, the border that came with the pattern will leave her with a quilt too big for her bed. The original design had a border 12 or 15".
There is an 1850s quilt on this blog post with a double dog tooth border. This seems a good solution (and a lovely running feather quilted up between them would look fabulous). Scroll down until you see the Old Otterbein Quilt.
There are a few ways of stitching a dogtooth border. Paper foundation piecing is the most obvious but this quilt is entirely appliqued by hand, this would be the wrong solution for this particular quilt. So here is my preferred way of appliqueing it.
For Linda's quilt the teeth are one inch high and one inch wide at the base.
This way of doing it ensures the tips of the teeth are all the same height (and a difference in height shows up far more than a difference in width).
If you are appliqueing by machine you can cut each tooth and glue it down, then stitch the row in one go. Just make sure you have a stitch at the top and reduce you stitch length and increase you width of stitch at the bottom between each tooth.