Where does the Constitution state that private individuals cannot set goals to hire minorites?
Ronald Reagan supported voluntary affirmative action.
What's the big deal?
The big deal is that we are talking about a Supreme Court Judge not about a business deciding to implement affirmative action programs on its own design.
Harriet Mier's words about wanting the Texas Bar Association to reflect the population of the state should be a tip off to her view on set asides. If she felt such a view was in conflict with the constitution she would not have advise such a position unless she chose to act counter to the constitution.
In either case she demonstrated herself to be outside of the order of a strict constructionist advocate of the constitution.