I am not the expert here; but I think she is correct, and her department was responsible for the security.
Ok she is correct to admit her failure, and she should resign.
Next is the matter of the cover up. That goes right up to the White House. After Hillary resigns; which she now needs to do, who at the White House will take responsibility?
Obama has to explain why he and everybody else saw the whole dang thing on video feed as it was happening, and Obama went to bed instead of ordering any help for this situation.
And why his first response was to apologize for that pesky freedom of speech that we have in America. And why he stuck with that story long after everybody knew it was a lie.