She’ll pick either an Afro American or Hispanic.
I don’t think she can; even Obama knew he had to sucker whites (including men) to vote for him, so he targeted the easiest to sway and picked a white “Catholic” guy (I say this as a Catholic). It certainly helped.
At this point (especially after the racial strife of the last 7 years), there are simply not enough blacks, Hispanics, and Asians to reach 51% of the vote (though we are rapidly approaching that point) - and that assumes those groups would even support Hillary. It almost certainly has to be a guy (even if he’s “riding in back”).