<p>You know what? Tell her you can destroy her future by informing Penn what she did with you. But go on to tell her that you won’t do it because you realize you were once good friends and that your conscience will never allow this.
She should know what you can do to her. She might not show it but she’ll ALWAYS feel guilty deep inside.</p>
<p>Or just take a transfer to Penn and give her a tough time. 
Haha, but I’m sure you won’t go through all that just to take revenge on her.</p>
<p>And make sure you’ve learnt your lesson. It’s going to help you in future ;)</p>