Sounds like she's not eating enough. I think it's better for her to STUFF herself on primal fatty proteiny food. Stuff her like Thanksgiving, to break her of the snacking habit and convert her metabolism away from sugar-burner. When she's feeling better, work on portion size.
Here's my meal plan.
Breakfast: Two hard boiled eggs and a Smoothie: berries, green tea, whey powder, bit of banana, and 1/12 a can of coconut oil.
(Whey powder is a bit of a misnomer on MDA, but it gets the job done for me. A whole can of coconut oil is total overload.)
Lunch
Ziplock sells a container which is three compartments and a lid.

It's plainly meant for a sandwich, raw carrots or something, and m&ms. Haha. I make ground beef in tomato sauce -- or chicken soup -- in the big compartment, a good veggie like kale in the mid-size compartment, and a starchy veggie like sweet potato or carrots in the small compartment. Plus a square of chocolate.
Dinner:
A raw or cooked veggie and a meat. My dinner meats are 3 oz canned salmon OR a can of sardines OR pre-cooked gluten free nitrate free sausage. (in the US we have a Jones brand.) That sausage is dripping with fat and fills me up.
Snack: butter. Yep. Grass-fed salted butter right out of the tub. After a teaspoon or so, I've had enough.
5'0" female, 42 years old.
Started Primal October 31, 2011, at a skinny fat 111.5 lbs.
Current weight: 101.5. lbs and holding steady. Spring yardwork here we come!
Co-worker 1: Needs to lose ~50. Now he wants to start Mayo Clinic Diet. Yeesh. Give it up, man.
Co-worker 2: Needed to lose ~55. Lost 20 from stress. Started Primal in Sept, lost 20 more, but gained 10 back on a carb spree. We're working on it.