If you want her to have a good experience,  just set aside an extra $100ish to make sure it is super comfortable for her. My kids had a blast. My wife found BYU outfits for them on marketplace for like ten bucks, and they were so excited to be dressed up. I kept them eating and drinking stuff the whole time, and it made them super happy to be there. They loved the cheerleaders and the cougarettes the most. They didn't watch more than ten minutes of football the whole game haha! They loved the marching band, fireworks, music, and getting excited with everyone else. The tailgating stuff on the south side of the stadium before the game is a must! Honestly, just keep her eating and drinking, and she will have a great time.