According to the Post:

 Bloomberg has tapped DC-based Marshall – who was President Bill Clinton's White House social secretary from 1997 to 2001. Under the Obama administration, she served as chief of protocol of the United States — a sensitive diplomatic position bearing the rank of ambassador — from 2009 to 2013.

Prior to that, Marshall was a special assistant to Hillary when she was First Lady in 1993. In 2006, Marshall worked on then-Senator Hillary Clinton's re-election and then joined her presidential campaign in 2008.

And:

 [A] Democratic source told Page Six, "Capricia Marshall is one of the very top people in Hillary's immediate inner circle, she is far more than a campaign person, far more than a political aide, and is a very respected insider in the Obama circle.