How can the husband be informed about relinquishing the Mahr, and is it better for the father or the wife herself to inform him?

The dowry is established for the woman upon the mere conclusion of the marriage contract. She has the right to waive it, in whole or in part, if she is an adult of sound judgment, whether by herself or by appointing her guardian as an agent. It is recommended that she consult her father for his experience, and witnesses should be present at the time of waiver.