Maybe she's a nerd, as well, and maybe she has different fears than yours - such as, a fear of you acting awkward and weird around her from now on. And so she's become a bit "defensive" around you, in case you have a secret plan to make things weird in public.
Maybe you should have left out that part in the email where you said you wanted to skull-fuck her corpse (bareback, natch) after slowly torturing her to death. Seems less creepy without that.
Also, don't ever ask someone out via email. Nerd.