She was talking about Crusader Kings, where if you fuck your relatives enough there is a chance to get a pure blood trait, that will reduce the chance of getting negative traits from it. However it's generally not a reliable way of building a superior race, as inbreeding without it will pollute your gene pool so hard you will spend more time trying to procure clean specimens to get rid of already existing bad traits, than you will trying to secure good ones.Matara is somewhat missrepresenting what actually happens in inbred populations, however. While genetic purging (Link) reduces the susceptibility of a given population to the negative effects of inbreeding, it strictly affects the population through natural selection (individuals with too many negative genetic traits don't reproduce). It does not, however, confer any kind of resistance to the negative effects of inbreeding to the individual. It's just dicerolls and statistics.