Getting The Right Portions

My girl came home, as usual, slimmer and more fragile looking again.  This is very worrying, as her mom, what I do when she comes back weekly, I will "nag" a bit, feed her with her favorite Japanese food and double steamed some chicken essence for her.  Other than that, I cannot do much.  If I could have my way, I would like to stay with her in the hostel... LOL.. I thought of buying her this portion control porcelin so that she knows how much she needs to eat daily and to make sure she gets all the right nutrition as well.  Sigh.. what can a mom do next?