What is the ruling on blaming a wife who preferred Buddhism over Islam, knowing that her husband was aware of her being a Muslim for a long time and that she performed all rituals, and does her accusation of him being rigid and extremist negate this blame?

The religion of Islam is the only religion that Allah has approved for His servants. It is the most complete of religions. Whoever believes that there is a religion better than it, or that it contains beliefs or acts of worship superior to Islam, has committed one of the nullifiers of Islam. Whoever says such a thing must repent and return to Islam; otherwise, the marriage becomes null and void, and separation becomes obligatory.