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.)
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.
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, 44 years old. Started Primal October 31, 2011, at a skinny fat 111.5 lbs. Low weight: 99.5 lb on a fast. Gained back to 115(!) on SAD chocolate, potato chips, and stress. Currently keeping food tracker.
I (try to) follow by-the-book primal as advocated by Mark Sisson, except for whey powder and a bit of cream. I advocate a two-month strict adjustment for newbies. But everybody is different and should tweak Primal to their own needs.