Complex sentence: Paradoxically, in post-war Poland she was suspected of collaborating with Nazis and with the help of an American UN envoy to Poland, William Opdyke, in 1949 she left Poland for the United States.
Split into simpler sentences: Paradoxically, in post-war Poland she was suspected of having collaborated with the Nazis. In 1949, with the help of an American United Nations envoy to Poland, William Opdyke, she left Poland for the United States.