The only thing I would worry about with the magnesium is if she is on blood pressure medications since magnesium also lowers blood pressure.
Here is my write up on fibromyalgia:
Fibromyalgia is a disorder of improper adenosine triphosphate (ATP) formation by muscle cells. ATP is the compound that provides energy for our cells and helps them to function properly. Magnesium malate and malic acid are recommended because both magnesium and malic acid help to increase ATP levels. Many health food stores sell combinations with both of these for this exact purpose. Otherwise I recommend 300mg magnesium malate 3 times daily. You can get malic acid at wine or beer making supply companies or online for about $4.50 a pound.
Fibromyalgia has also been linked to low serotonin levels. Chamomile is the richest source of tryptophan, the precursor for serotonin. Therefore, drinking chamomile tea frequently before meals can help elevate tryptophan levels. The tea it best drunk on an empty stomach because larger amino acids can block the absorption of tryptophan or block its conversion to serotonin. The supplement 5-HTP is the intermediate for serotonin production available in health food stores. It should be taken on an empty stomach as well. About 80% of the body’s serotonin is produced by the intestinal flora. Using probiotics. Such as kefir, and prebiotics, such as FOS and other fibers, will raise the flora levels and thus raise serotonin levels.