Unfortunately, many of these answers are incorrect. As this could potentially be an issue with legal ramifications, it is important that your friend also be in contact with a lawyer regarding any criminal accusations or charges.
On the issue of diplomatic immunity, the answer is an unequivocal NO. Diplomats have diplomatic immunity, consuls and consular officers have limited diplomatic immunity, but family members enjoy no such protection anywhere in the world, regardless of rank. Even wives or husbands of ambassadors are not granted diplomatic immunity.
A US diplomat is an individual nominated by congress and confirmed in writing by the president of the United States. While family members may legally hold a diplomatic passport, and may be entitled to certain limited rights as a holder of a diplomatic passport, they are never extended diplomatic immunity.
If your friend is a Filipino citizen living in the Phillippines, she is subject to any and all laws. Her husband cannot intercede for her, nor can he use any diplomatic privileges to block her sentence (or, for that matter, prevent her from getting a divorce or keeping custody of her children). Diplomatic immunity simply prevents a diplomat from prosecution by the government of the country to which he is accredited.