Let me preface this by saying I don't support Hillary Clinton and I think she has done a fantastically miserable job at being honest with the American people about her role in the whole scandal.

That said, "classified information" being shared on her email is a non-issue. First, there were I think something like three Confidential-level sentences in the tens of thousands of emails that she sent or received. Those emails were not properly marked with a classification header and footer which must accompany all classified material - basically, a big, bold, red headline that says CONFIDENTIAL, along with any special handling instructions. Because those headers and footers weren't sent to her in those emails, it is reasonable to assume that she believed she never received any actual classified information. (It would be easy to skip over a "(C)" if you were skimming through the email, or if you were not paying close attention, etc.)

Second, Confidential is the lowest classification of information in the USG. Believe me when I say this, any information that's classified as Confidential is not very important and could probably safely be unclassified.