Via state.gov:

Mary Elizabeth Taylor is the Assistant Secretary for Legislative Affairs for the U.S. Department of State.  Previously she served as senior advisor in the Office of the Counselor.  From 2017 to 2018, Ms. Taylor was Special Assistant to the President for Legislative Affairs at the White House.  In that role, she led the process and strategy guiding Senate nominations, spearheading the successful confirmations of more than four hundred nominees, including the high-profile confirmations of Supreme Court Justice Neil Gorsuch, Secretary of State Michael Pompeo, and CIA Director Gina Haspel.  Previously she served in the office of United States Senate Majority Leader Mitch McConnell, working on the Senate floor as the Senior Cloakroom Assistant and acting as a liaison between the majority and minority leadership to negotiate agreements on legislative and executive matters.  Ms. Taylor also provided Members of Congress with parliamentary advice and counsel on floor strategy during consideration of pending legislative matters.  A Washington, D.C. area native, Ms. Taylor holds a B.A. degree in political science and Spanish from Bryn Mawr College.

The Bureau of Legislative Affairs (H) coordinates legislative activity for the Department of State and advises the Secretary, the Deputy, as well as the Under Secretaries and Assistant Secretaries on legislative strategy.

I’ve confirmed this resignation with a person familiar with the issue. Quite the shock at State, where the info is close-hold and many have not been notified. https://t.co/amNteLf5bA

— Nahal Toosi (@nahaltoosi) June 19, 2020

Highest Resignation in Trump admin. over handling of #GeorgeFloyd + Racism

• Mary Elizabeth Taylor
• A. Sec. of state for legislative affairs
• Previously aide to Mitch McConnell
• Also worked at White House
• Unimamously confirmed in Oct. 2018 https://t.co/k77p44u73J

— Joyce Karam (@Joyce_Karam) June 18, 2020

Three senior women in the Trump admin resigned this week:
– Mary Elizabeth Taylor, assistant sec of state for legislative affairs
– Katie Wheelbarger, acting assistant sec of defense for international security affairs
– Elaine McCusker, deputy under sec of defense (comptroller)

— Elizabeth McLaughlin (@Elizabeth_McLau) June 18, 2020

Mary Elizabeth Taylor, the first black woman to serve as assistant secretary of state for legislative affairs, has resigned from the State Department in protest of Trump's response to weeks of nationwide unrest over the killing of George Floyd.https://t.co/73C7ngDP1v

— Axios (@axios) June 18, 2020