Does yoga make you lose muscle?

So I'm 15 and 5,3 and I'm generally skinny except for when it comes to my calves. My calves are huge and muscular in comparison, so they just make me look shorter which I don't need. I was thinking about taking yoga classes to stretch them out, but will it make just gain more muscle or what? If not, is there another activity? I'm not losing to look weight since I'm only about 100 pounds. Please no comments about how I should embrace my body.....by the way my calves measure at about 13 inches if that helps.