Sock wt yarn, or maybe even sport wt, if you need the perfect color match, and in an 80/20 or 75/25 blend of wool/nylon. The nylon adds to the sock's wear-ability. Would hate to have her do all that work, then have your toe or heel wear a hole in her good work.

But you might need to get a 100% wool, to get the right color(s). If that's the case, use something to re-inforce the heels and toes. Some yarn shops sell little cards of 80/20 re-inforcing yarns in a variety of colors? or I think you can use serger thread, called wooly-something? Maybe wooly nylon? Straight nylon can cut through the yarn over time.

Sweet talk her.