The norm in Silicon Valley is treat D&I with an inordinate level of skepticism, if not reject it outright as "anti-meritocratic." What we have here is not explicit racial segregation, but a system operating via capital and clout that has elevated a small group of mostly white men into positions of extreme power and influence over the most vibrant segment of the American economy. This creates huge bind spots and carries the risk of building systems that reinforce oppression.
>D&I may very well be operating at the wrong end of the pipe.
Then that should be the argument at hand. Not rejecting the idea outright.
>she was pressured into hiring an incompetent person
That there is no system in place for addressing concrete performance issues in any employee is the failing of the organization. The requirements for any role you hire for should be clear, expectations should be set and when they are not met there should be consequences. If this is not the case at the organization she worked at, she was bound to burn out, irrespective of the DEI objectives.