Is it normal my girlfriend doesn't believe that i'm a virgin?

I am a virgin and never been in a relationship but somehow met a really awesome girl and we started talking about stuff and she kind of became like my girlfriend. I still don't know how that happened because she is super good looking and beautiful and smart too and I am really totally lame. She is almost two years older than me. Maybe she liked my personality. One day I was in her car and I don't remember what we were talking about but I mentioned that I was a virgin. I don't know if she was pretending but she seemed very surprised. I only realized she was joking when she came close to my face, whispered in my ear "I would love to be your first", licked my ear, winked at me, and gave me a kiss. This seemed really dramatic even though it turned me on and gave me a boner but now I'm worried she might be a slut or whore and have an STD.