There are different categories of lies, based on intent and consequence. Hillary was branded a "liar" largely because of her sniper story... a bit of inconsequential self-aggrandizement based on fact. Trump's lies, on the other hand, are far from inconsequential... they are designed to stoke hatred and discord... the thousands of Muslims cheering on rooftops on 9/11, for example. Obama's birth certificate... and on and on and on.
Even if untrue, which is highly debatable given the rules for classified emails, she had more than sufficient cause to believe she was speaking truth.