How do I talk with my daughter about her weight

My daughter is 16 and in the past few years has put on weight-she should be about 20 lbs lighter. I work hard to keep healthy food and make meals that are lower calorie but she can buy her own food now. I was harassed by Dad about my weight as a kid and I wasn't overweight so I have some emotional issues with this subject.
The other problem is that my son has the opposite problem-he is 30 underweight and his Dr and coaches want him to gain. He is teenage boy and always hungry. I want to have high caloric foods available for him but if they are in the house my duaghter will eat them.
I try to say nicely things like "don't just eat from the bag put a few in a bowl" but she shoots me ugly looks and points out I don't ask the same of my son, which I don't cuz he needs to eat more.
What can I say to my daughter?