Calling anyone “a female” is arrogant, reductive, and dehumanizing. When someone does this, I suspect they have a strong bias against women, and I look for (and usually find) additional evidence of this bias.
At best, it’s bizarrely clinical and awkward, unless followed by an actual noun, like “female gamer,” but why are you discussing gender anyway? Hopefully to fight stereotypes, and not play into them.
Not convinced? Read “Stop Calling Us ‘Females’ for Real, Though” by Ashley Velez.