For one, if she “anonymously” donates to charities, how would anyone ever attribute any donations to her??
For another, as a sibling comment points out, AOC can have a much greater impact by influencing policies that help the people than through charitable donations, which, let’s face it, are just a bandaid on the structural issues that lead to such wealth inequality. Making something one’s professional goal when in a position of influence is much more impactful than optional activities on the side like charitable donations.