I too, wanted to be skinny, and be able to wrap my legs around the back of my neck. Well, I never slimmed down to anywhere near as skinny as she is, and I never could wrap my legs behind my head. But what did happen, is that I am now able to bend over and touch my toes, bend my body backwards and forwards without grunting, and without being in pain. So many of my friends and collegues in their forties, can't even bend over and touch their toes, without grunting like stuck pigs. That may not seem like much, unless you try to do it, and you can't.
Yoga strengthens the muscles of the mind, as well as the body.
I urge you to try a yoga class and notice the difference in your breathing, and in your life. That one class has made a considerable difference in the quality of my life. I am not always at peace with every situation in my life, but I am aware of the changes that my body is experiencing in a stressful period. That awareness of stress, and how to handle it, can easily diffuse a harmful damaging environment. I still practice my breathing techniques, even though I don't always practice the yoga stretching exercises on a daily basis.