This manipulative thesis is spread by various pro-Kremlin speakers, followed by the Russian media. Russian propaganda also says that, in addition to Ukrainians, the "collective West" allegedly intends to sacrifice residents of the Baltic states and Poland.
As StopFake writes, the call to "fight to the last Ukrainian" is attributed to British Prime Minister Boris Johnson. In fact, Johnson did not call on the Ukrainians to die; on the contrary, he warned the Russians that they would defend their country - and if necessary - to the last drop of blood. The leaders of the G7 also did not push Ukraine to fight "to the last Ukrainian"; instead, they expressed their readiness to share the burden of this struggle and pledged to provide Ukraine with indefinite support in defense against Russian aggression.