As someone who does grassroots campaigning, I’m not sure she can. She needs to reach out wherever her audience is.

You're correct in a moral sense although I agree entirely with other posters that politicians need to spread their message far and wide regardless of platform. I do not personally use Facebook or Twitter because I find them to be toxic, predatory, and privacy red flags in the case of Facebook. I rarely use Reddit out of principle when they screwed over Boost devs. The issue though is similar to why boycotts really just don't work for the left. Our power is in changing the systems at the government level, not at the endpoint or point of sale because almost definitionally we're not part of the 1% who make or break companies financially. Increasingly even together in unity that's still the case that our financial incentive offering is relatively minimal to the biggest companies if you ignore mass indignation as a stock value factor.

Twitter doesn't comply with hate speech laws on social media companies and is used as a tool by Elon to manipulate markets. These are problems addressed through giving teeth to the agencies and that's always going to be far more meaningful than the 4 cents you contribute in ad revenue before you max out views for the day.

Let's be honest though, with Twitter it's going to fail with or without government teeth around it. Elon has already started prepping the narrative to why his white nationalist pickme project is death spiraling.