Has she has another TTG? It appears that she may be getting gluten somewhere.
Gluten intake and low Vit. D are two different things and one doesn't necessarily have to do anything with the other. I assume that being in So. Cal means you get plenty of sun? Did you augment the Vit. D intake when you went gluten free? There is a chance of there being gluten introduced into her diet- Is she having any of the symptoms she had before? If not, I would suspect a general need to up her intake.