I think she is too but that would be too obvious, no? When she had Dexter check out her place (pretended she was scared somebody broke in) it was clear she just needed him to find that disc. i think she was the 1 who shot that guy on that tape.
it definitely does seem too obvious! i agree. you just never know though! I am really liking the way they are setting this up though. I haven't been this invested in a storyline since Trinity!