Black men couldn’t stand Hillary and black women were just slightly less put off by her. A screeching white Yankee is a turnout problem as 2016 demonstrated and it’s probable that Latinos will also take a dim view of a schoolmarm in her flats and cardigans.
In theory she could try to boost black support by picking a black person for VP, but it is hard to see how any of the obvious choices would help the ticket (Spartacus, Kamala, Al Sharpton, Stacey Abrams, Al Green, Elijah Cummings, Maxine...). A ticket with no white males on it would be a first.