What would you do in this situation?

Okay, so I ride the bus to school in the morning. There are no other options. Anyway, I'm the first one on the bus and I usually sit in the back. No matter what seat I choose, the girl who gets on after me always sits directly in front of me. When her boyfriend gets on the bus, they get a bit "cozy" (we're talking extreme PDA here) and talk loudly about videos they watch where people put paper cuts on each other's eye. I have a pretty weak stomach and seeing and hearing all this graphic stuff does not do me any good on the hour long ride to school. The problem is that by the time the boyfriend gets on the bus, there are no seats left so I can't move. And I can't really move right after she gets on because we're the only two on the bus, so she'd figure it out and get offended. And she's not the type you want mad at you... What would you do in that situation?