Hillary will not apologize for voting for the Iraq war. She ought to, but she won't. She says if she knew then what she knows now, she would not have voted the way she did. What she didn't know then was that the war would become so unpopular.
The big issue here is her judgment. Why didn't she know then that the war was a mistake? Lots of people did and rightly predicted what would happen. She made a wrong judgment when the evidence against her vote was available for all to see. She went along with Bush and made a colossal error of judgment.