3) If the virus spreads to the world and starts killing off seniors everywhere and then China gets caught then they will be the international pariah with only maybe North Korea as its ally.
US has a strict policy where any bio/chemical weapon attack is treated the same as a strategic nuclear attack and it sparks off WW3.
If not that then at least China's progress gets rolled back 50 years as US already has a hard-on for China now.
While I don't believe that this contagion was devised by her, I also don't think anyone would be able to do much even if they did.
It's too ambitious of you to think that USA will be able to do much even if they find something concrete supporting their motion. China holds about 10 percent debt of USA in treasury bonds. If she ever were to liquidate it, USA's economy would plummet at a rate much steeper than 2008's, which won't end well for any country in the world.
China exercises significant influence over just about every country you can imagine. Sure, communal anger may make companies migrate their shops elsewhere which would affect China to a considerable extent but again that's as much it would be affected by.