^^^Does SpaceX have the hardware and staffing necessary to do a short-notice manned mission?
They appear to have 3 operational Crew Dragon ships right now. One is on station already, another is at the Cape in preparation for launch on Polaris-1. That one does not have an ISS compatible docking collar on it right now, instead having a hatch designed for EVA work to test SpaceX's new EVA suit they have just designed. The final capsule does have the original ISS compatible docking collar on it but I don't know its mission readiness.
Honestly the simplest solution to all of this (if Starliner is unfit) is to have Butch and Suni shelter on the ISS until the next scheduled Cargo Dragon mission. NASA can then send up a Crew Dragon rather than Cargo variant, with only 2 seats installed rather than 4. The remaining space is used for supplies. Butch and Suni then come down on the Crew Dragon.
Minimal cost to NASA, minimal operational interruption to the station's supply chain.