Years of character assassination and relentless allegations don't actually make someone an inveterate liar if most of it leads to nothing significant. Hillary Clinton being a "liar" is mostly a product of years of hard work by GOP strategists and for-profit media who want flashy headlines. (Yes, Clinton has taken some liberties with the truth, but less often than most other politicians.)
As a matter of fact, apparently the "liar" allegation-turned-meme goes all the way back to when Clinton was as a 27-year old lawyer investigating Nixon. To discredit her after the fact, the allegation was made that she was fired from the Watergate investigation. That allegation has never been proven, and in fact, it is provably false. But right-wing TV and radio hosts repeat it over and over again, along with all the other allegations, as if the weight of allegations themselves, despite being created by those with a motive to smear her, could be construed as truth.
Call it another win for The Big Lie strategy. Add it to all the other wonderful outcomes Big Lies lead to. Or shake it off, and try to find the truth, which I grant you is a nuanced and complicated picture of a human being who is no saint, who's made mistakes, and who's a politician. But someone who is a far cry from Evil Incarnate.