Ms Sherman - the US Deputy Secretary of State, one of the department's top positions - has been meeting Russian officials this week to discuss Ukraine.
US officials are hoping to defuse the tense situation through negotiations with the Russians - and Ms Sherman is in her element.
Known in Washington for her spiky manner, she has a history of tackling tough subjects head on.
She developed her diplomatic skills in an unusual manner: after studying at University of Maryland School of Social Work she helped children in Baltimore who needed foster care.
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