There is no "normal" weight for people anymore, as everyone has a different build and these days, because more people exercise, they carry more muscle, than in the days when they didn't. This means people are heavier now, but not necessarily overweight.
Weight is personal to the individual and people should be the weight they feel comfortable at. If you keep focussing on your daughter's weight, you will give her a complex and she will probably end up with an eating disorder. So many teenage girls are obsessed with their weight and size now, that many have eating disorders and low self esteem.
If you are concerned about your daughter's weight, don't keep mentioning it to her, but purchase healthy option foods and make her healthier meals. You have no control of what she eats outside the home, but you can provide a healthier diet when she is home.