I think this way of eating is healthy even for those who don't need to lose weight. At that size, she probably won't drop much if any during Induction anyway.

I am NOT medically trained in any way, so you might want to consult an expert, but I think if she wants to try Atkins she can do a two-week Induction (essential for breaking addictions to sugar and carbs) then rapidly progress through OWL. Maybe adding 10 grams a week instead of 5, or even more. I have heard that this WOE "stabilizes" your weight, so that if you're overweight you lose and if you're underweight, you might even gain a little until you're at a healthy weight.