UMD-737 - My friend's girlfriend snuck into my bed! 'Hey, want to do it? No one will know if we're under the covers.'

Never touch your friend's girlfriend, but after a house party, she ends up staying over. Once the boyfriend passes out, she sneaks into my bed. She starts whispering, 'What do you think of me?', 'Ever thought about doing it with me?' How am I supposed to resist this?