What offer does tio Luis make to mama? How is she more than adamant that this offer will never be agreed to?

Tio Luis offers marriage, a powerful marriage that if he won the election for governor would make her a governor's wife. Mama refuses him outright, telling him that his offer offends her.

She stood up and spoke slowly and deliberately. “I have no desire to marry you, Luis, now or ever. Frankly, your offer offends me.”