I think your focus is misplaced. When a department accepts grad students, they are looking for people who are ultimately going to be doing research, co-authoring papers, and speaking at conferences. While they may have some idea about diversity as a goal, that’s going to be secondary to accepting the best students they can (which could mean different things, whether it is obvious metrics of academic achievement, or some unique interests backed by letters of recommendation).
This is in contrast to their undergrad admissions. Undergrads are there to take classes, and form more of an aggregate as far as the university is concerned. For graduate admissions, the question is really whether you look like you will add to the department’s research output. Put in your best application and let them worry about how they came to their decision. (Note: I have a PhD and can speak from some experience at least with respect to my own field.)