How can my brother's wife be convinced to abandon the ideology of the "Habashis" group, and what is the response to their accusations that Salafis are "takfiris"?

The Habashis are a deviant sect, and one must beware of them. What your brother's wife mentioned, that Salafis excommunicate people, is false. Excommunicating a Muslim without proof is a grave matter and one of the major sins. Only innovators fall into this, and this is the methodology of the Habashis. We advise referring to the book "Al-Radd Al-Wafir" by Ibn Nasir al-Din al-Dimashqi, and examining what has been written in refutation of this sect, including what was written by Professor Abd al-Rahman Dimashqiyah.