China puts targeted sanctions on the State of California and Pelosi's donor network. They mimic US language of oligarchs and foreign interference repeated ad nauseum by US media and government. They outline her financial interest in Taiwan and abuse of power to become wealthy during her political career. The PR campaign and heavy sanctions work to politically isolate her from allies and neuter her influence, she's left out to pasture to "Spend more time with her grandchildren" shortly after the election where Democrats get obliterated.
The stupid imperialistic gesture finally ends the reign of one of the worst neo-liberal ghouls of a generation and China stays winning.
Against whom? We're a bit far from China straight opening fire on US navy or aircraft. And I don't see any proxies in the region who would be worth the conflict. This isn't like Ukraine, where you've got a sizable chunk of Russian-aligned nationalists sitting right on your border that you can just step in and annex. China's already either allied with or a major business partner of all of its neighbors.
If anything, I might see them try some kind of Cuba-style embargo of Taiwan. But that would have a comparative impact on public sentiment, driving the island that much farther away from the Chinese political and cultural sphere.
So long as the US and Taipei are allies, the US absolutely can. What Beijing needs is a large anti-colonial movement in Taiwan, akin to what they had in Hong Kong. And they're decades away from anything close to that kind of political hegemony. This is just going to be an indignity they'll have to endure, until Pelosi (or her Republican replacement) trips over their own balls trying to Own The CCP and turns public sentiment against the US.