I would add that I was not on board until the attacks in Belgium. I was unsure if I'd support Bernie, Hillary, or other. But after being disappointed with Bernie's Daily News interview (he sounded so unprepared and questions were not hard), he then uttered generalities. Hillary set out a clear list of actions. In an imperfect world not all would work but she sounded like the adult in the room.
I also think some of her secretiveness, which I agree looks bad even when she does nothing wrong, stems from 30 years of relentless and often vicious attacks. She's been brutally attacked for her looks, her education, her daughter at age 12 ridiculed as "ugly", she's been slammed for routine comments or actions, her marriage publicly dissected, she's been lied about repeatedly and the lies accepted as unvarnished truth (most recently that Debbie Wasserman Schultz was offered a high level position in her campaign after being dumped as DNC chair, DWS was offered an honorary position with no power or duties). So Clinton tries to put a protective fence around herself. As for the email, other Secretaries of State did the same but it was never an issue in the Bush Administration. During the Bush Administration there were 20 attacks on embassies resulting in over 60 deaths, including an ambassador. No Congressional investigations. And if the DNC had paraded the family members of the victims they would have been rightly slammed as cynically manipulating.