She is indeed perfect for the job. I believe she enjoys it, too. She enjoys the control she exerts over the press corps. I've read interviews where she expressed her contempt for liberal intellectuals, as well as resentment for the way she was made to feel like a poor relation by DC insiders when she ventured north before she was appointed Trump's press secretary. She has both a chip on her shoulder and an axe to grind.
Sanders is in the catbird seat. She can put the press in their place - remember how she jerked them around with her long-winded beer parable the day the Manafort indictments were unsealed? Or the day she made reporters list the things they are thankful for before she would answer their questions? There's a measure of payback in both her control and her steadfast, and sometimes insane lies. This is her chance to stalwartly defend the President, as well as her own political ideologies against the liberal press, whom she regards as hostile, while at the same time, 'keeping them in their place'. This is probably the best job she'll ever have.