I agree with Niadalla. Unless she is hugely overweight to the point where it is unhealthy I would be backing off. Her same-sex parent putting so much emphasis on her weight is not a good thing, regardless of whether or not it is motivated by concern. I guarantee she is fully aware of it if she has weight issues, the kids at school and modern media would have made sure of that, and she doesn't need someone who is meant to love her no matter what sending the unsaid message that there is something wrong with her. If overeating is emotionally based it will not help. If it is based on rebellion it will not help. The best thing you can do is provide a good roll model, and allow her to follow when SHE chooses to.