Not sure actually HKKMR, I wouldn't stop any partner from eating stuff she likes.
What I used to do was plan for my ex, she'd tell me what she wanted to lose and i'd work out a diet "sonja bakker" style with what she'd eat when and what sports she would do. I wouldn't really monitor it, that was too much hassle, but it worked because she had set the goals herself. Not sure what your SEI really wants or needs though, my ex wasn't SEI so...