She will be staying, and that's just one of several reasons why he should stay as well. He's going to go into the NBA already a multimillionaire after 2 years at BYU, and he wisely values one more year at the school over the opportunity to make a few million bucks more down the road. The argument that he might total $250M in the NBA if he left now, but only $235M if he stays another year at BYU, to him sounds like a no-brainer reason to stay another year at BYU. He wants at least another year of education, to marry his girlfriend, to improve his own skills on the court, and to win a natty.
The NBA can wait. He's staying.