Knitting with stretchy yarns

Dear readers,
A while back, my mother-in-law revealed a shocking piece of information. While my mother-in-law loves to knit, she is allergic to wool. Oh, the horror!
At the time, I was working on my mother's beautiful koigu socks. Koigu is made from merino, but it doesn't feel like wool. Not at all. Nevertheless, Jane (my MIL) stated her opinion that it was still scratchy (I'm really hoping that this wool allergy is not hereditary*).
Yet, being a thoroughly converted sock knitter, I still wanted to knit socks for Jane.
I found this delightful cream colored yarn- a cotton-lycra blend. It was stretchy and soft, unlike most cotton. I decided to purchase the yarn, intending socks for Jane.

I've started the socks, and friends, it is not pretty. The yarn is pretty enough in color and texture, but it stretches horribly. Which makes getting gauge impossible. I'm unsure if the socks will even fit her. Here's hoping, though, because I am loathe to frog the whole sock that I now have down to the middle of the foot.

I'm working on a cabling pattern, too, which complicates things in unanticipated ways.

I knit on the socks while I was in New York for my sister-in-law's wedding. It was beautiful, by the way. And the lace shawl that my MIL made for my SIL turned out to be gorgeous. It is definitely heritage knitting.

*Perhaps there should be a questionarre for potential marriage partners that includes the question: Does anyone in your family have a wool allergy?