Eh, maybe she was just looking to hook up and nothing more? Maybe you started emailing her and she felt trapped, like you wanted something and she didn't. Listen, some girls are just as horny as males, and behave the same way as males when it comes to hooking up and sex.
Women are by far the most secretive, sly, and downright bitchy beings on this planet. You NEVER know what's going through their minds. So, honestly, unless you are hung like Peter Rabbit, then I wouldn't worry too much. Forget her, go find yourself some other broad.
Also, word of advice, don't play the dating game over emails and online. It only begs for trouble. First of all, you don't see each other, and what's the fun in flirting through typed words on a screen? You want to see her when she blushes, and when she gets turned on by you. Most importantly, you can never tell when people say things what context they are saying them in. It's really easy to get pissed off at someone for saying something over the internet because you don't know how they mean it, than it is in real life.
"Bangkok Tower, United 890 Heavy. Bangkok Tower, United 890 Heavy.....Okay, fine, we'll just turn 190 and Visual Our Way