I HATE BEING SINGLE!!!
Sound like a "let it go" case to me.
If you can't, obviously the email route has failed.
Because she just broke up with her boyfriend, she was probably feeling vulnerable and in need of the company of a friend like you, which led to your date. I'm thinking that afterwards she realized she accidentally led you on, and is probably avoiding what she feels is inevitable: you confessing to her, and her friendship with you forever gone.
It would be nice if you got a hold of her, and asked her what's going on in her life: ask casual things, don't spring anything on her, and from this you can probably figure out how she feels.
I agree with >>48 that it'd be best to let this one go, but just talking to her and getting some closure would help.