Legal Question in Family Law in California

U.S. laws and U.S. courts would have nothing to do with this. It is entirely a matter of German law. Place of residence, not place of marriage or citizenship, is what determines what divorce law applies and what courts have jurisdiction. She could move back to California for six months and thereby re-establish U.S. residency for divorce purposes, but unless she brought the children, the U.S. courts would still defer to the German courts and law if the husband filed proceedings there. Only if she and the children move back to the U.S. together six months before filing for divorce, would the U.S. courts exercise jurisdiction.