Girlfriend's friends think I'm prude...?

THey are 2 years older than us and my girlfriend and them are very close/ Anyways when i first met them i was a little shy because they were guys too and i had no idea what to say so i just kind of stood there lol. Anyways tomorrow we are all hanging out and she said they think I'm probably really prude and that kind of hurts cuz im not at all. How do I change their minds and give serious answers cause i dont wanna hear "rape her" or anything like that. Anyways also what should i talk to them about and how do I let them accept me????