Tomas knows that if he turns down the job offer, it is for Tereza's sake.
During the first week of the occupation, she had gone around the streets taking pictures of the Russian tanks and giving the film to foreign journalists. She seems almost happy.
But she tells Tomas that she would be fine with leaving the country with him. The "general euphoria" of the first week of occupation quickly turns to "drunken a carnival of hate" (1.12.9). Alexander Dubcek, the temporary leader of Czechoslovakia, has returned to Prague from Moscow, having been put under the thumb of the Russians.
It's clear to Tereza that her country has to submit to Russian forces.
Tomas asks if Tereza is bothered by the fact that Sabina has also immigrated to Switzerland. Tereza responds that they will be in Zurich while Sabina is in Geneva, so she will be less trouble than she was when they all lived in Prague.