Race is not simply a social construct. There is a strong biological component to race caused by recessive and dominant alleles and phenotypic traits. Biodiversity is biological, and it can be tampered with by science. Gender is a social construct by the way. I think you meant ***.
You give her crap about not experiencing the struggles of black people (which I won't argue), but do you think Caitlyn Jenner really knows what it is like to be a woman? Would he know what it's like to give birth, to have an evolutionary drive to create and nurture life? To experience a menstrual cycle? Hot flashes and menopause? Embarrassment of bra size in middle school gym class? To get paid less for doing the same job? He's a rich white man and an Olympic athlete. He may think he does, like this girl thinks she's black, but they are not. You accidentally proved my point. There is a lot more to being a *** or a race than just messing with hormones and skin pigmentation. There is a social aspect to both that coincides with the genetic component. You'll never truly be both unless you were born that way.
Race isn't a simple social structure. It's complex one. People either need to disapprove of both, or support both. If you pick one or the other you aren't being logical.