What is the religious ruling on killing a mother who converted to the "Jehovah's Witnesses" religion after embracing Islam and is now working to convert her children to Judaism? Is it permissible to kill her to avert her fitna (temptation/strife), and if not, what should be done?

This mother, who has apostatized from Islam, has no legal right, according to Islamic law, to the custody of her children. It is your duty to rescue the children from her by every possible means permissible by Islamic law. You are not permitted to kill her, as that would entail corruption and the abandonment of the children. If you are unsuccessful in removing them from her, then you must look after them and work to prevent their mother from influencing them, and your kindness towards them may lead them to prefer your religion over their mother's. We caution against the danger of being lenient in residing in non-Islamic countries, due to the risks this poses to religion and morals.