Well, remember that most football games are on Saturdays so first step would be for her to check their online schedule. Also, I know with Ohio State games, certain ones will be sold out months in advance (The OSU/Michigan game is insane to get tickets to) so if the website doesn't sell tickets there, try calling the box office. If push comes to shove, she can find scalpers outside of the game also though that will cost a bit.
Ok, you've assumed way too much there already. Didn't know they were mainly Saturdays. What is the best site to buy tickets.
Stubhub.com