Aren’t governments able to refuse a person as ambassador? I believe it has happened before.
Before a President publicly announces a nomination for Amb that must be confirmed by the Senate, the name is submitted to the host government confidentially, which must provide agreement to that nomination. Thus they have veto power over who can be the ambassador.
After an ambassador is at post, the host government can ask Washington to remove him/her for a particular reason. Almost never is it done thru the PNG process. Hume Horan our Ambassador to Saudi Arabia was removed by the former process. He was a sacrificial lamb. Horan was acting under direction from Washington to upbraid the Saudis on the importation of Chinese IRBMs without our knowledge. The WH backed away when the Saudis became upset with what the Amb said. The WH claimed that Horan was acting on his own and he was immediately reassigned from the Kingdom by Washington.
Anne Patterson is doing what Washington is directing her to do.