When NRI brother gives money to Resident Indian sister, what should be the procedure?

Brother is an NRI running a business abroad. Sister is housewife in India. Since she doesn't work, she doesn't file taxes.

Brother wants to gift around 10-15 Lakhs to sister. I don't think there is any tax liability for this, but how should it be handled? I am assuming sister would need to file taxes in the year she gets the money. Does proof need to be shown that it's a gift from the brother? How should it be shown?