She set up private email servers, completely and deliberately ignoring people telling her how to set up the security on it so that it wouldn't get hacked. Both of those things are illegal if you're handling classified information, which she knowingly was. And then it got hacked, and now highly classified info, some of it so classified that the US government can't even hint at its existence, is now in the hands of foreign enemies.
So yes, she should go to prison.