It’s more than an individual choice. Kamala Harris represents the growing political power of women, and Black women in particular. Black women are an important demographic in America. https://www.nytimes.com/2020/08/12/opinion/kamala-harris-joe-biden-election.html
No other major demographic is as loyal to either party as Black people, according to a 2018 Pew Research study https://www.pewresearch.org/fact-tank/2018/11/08/the-2018-midterm-vote-divisions-by-race-gender-education/
Of course this moment was a long time in coming. A century ago, this month, women got the right to vote in the 19th amendment. Now momentum is afoot in gender equity. And that is good for all women.
As the saying goes, all ships rise with the tide.