Historically speaking, coups happen more when a head-of-state leaves the country. Imagine POTUS is in Paris and Pence gets shot. Pelosi grabs control, bars POTUS from returning.
Unlikely, I know, but they're freakin' DESPERATE.
The SoCal shooting looks suspiciously like a MKU hit on witnesses to the LV shooters. Too many off-duty cops just happening to be hanging out (6) around 3 witnesses for it to be a coincidence. It doesn't pass the Red Face test.
It wouldn't be her initiative - Cabal-backed. She gets herself sworn in on the Capitol steps, declares an emergency, and forbids POTUS from returning. CHINA immediately recognizes the legitimacy of the regime, and possibly Russia. Military mostly backs POTUS (particularly Navy, USMC) while Pelosi tries to convince NG troops and AF to back her. Hilarity ensues.
It would be a fucking shitstorm, de facto civil war. But, as I said, they're desperate.