Intentions of this girl, please help?

I need help understanding a girl. I met her through my friend and this is all online. We've been exchanging photos and she said she would like me to DATE HER. However I have a Girlfriend and she keeps refusing to give me her mobile. I just wanted to text her. Now I haven't heard from her in 3 days. I know she likes me. She's ignoring my emails and that is all I can do to contact her, all I have is her email. Her last email said 2 words "date me". What do you think she is up to? Mind games? Toying or is she for real? She's 20. Im 23. Im in NYC, she's in PA.