The story
He gave her place to her sister and forgot the calendar.
Grant rejects Mara in front of both tribes at the mate selection ceremony, hands her position to her crying younger sister and promises it is only temporary. What he has not counted is the three days until Mara turns twenty two, after which tribal law takes her right to choose and she goes where she is assigned, which is to the dying Dragon King. Grant assumes her father will stop it. Mara accepts. Three days later, as he arrives to bond with Brenna, a hundred dragon guards reach the Hale gates for their future queen.