Nope. She's a fine weight. Of you look at her skeletal structure it is much smaller than average (tiny shoulders, petite build). It's fine for her to be a little thinner than average.  I'm 5'6" and I like how I look best when I'm just on the cusp of "underweight". Anorexia is when you are 20% below a healthy level. Of you just want to be skinnyfat sometimes, slightly underweight is okay. If you want to workout and get somewhere in the normal range due to muscle growth, that's fine too.