Early-graduate teen sim can't go to university?

The other way you can get her in is to use the mailbox cheat. Right click on the mailbox and select University I think it is. There is a command where you can enroll a Sim to university. I just took three Teens who had graduated early through University, so I know it's possible. Use the cheat. If your Sim earned the Scholarships applied for that will show up upon enrollment.