St. Thomas University signed two local women to its inaugural flag football team for the 2021 season:  Miami Lakes resident Tiffany Walker, a  graduate of Barbara Goleman Senior High, and Christina Mathieu from Miami Gardens, a Monsignor Edward Pace High grad.     Walker, a wide receiver and safety, was the second student-athlete to commit to the new team; Mathieu, also a wide receiver, was the first.     They were chosen as members of this...