Is it permissible to give money to a smoking mother for her to buy cigarettes, in order to avert her anger, knowing that it is forbidden to assist in sin?

Smoking is forbidden due to its harm, and its prohibition is indicated by the Hadith: "There should be no harm nor reciprocating harm." It is not permissible to assist in its purchase due to the prohibition of cooperating in sin and transgression. You must continue trying to convince your mother to quit by explaining its harms and the fatwas of scholars, seeking advice for her, and treating her with kindness.