This is the overlap note. The appointment itself is on the FISC-amicus post: Georgetown lists her as a statutorily designated amicus for FISC and FISCR; contemporaneous reporting dated the appointment about April 15, 2021.
The Administrative Office of the U.S. Courts Director’s Report on FISA court activity for calendar year 2021 lists Mary McCord among six individuals appointed as amici that year (seven appointments of six people: Amy Jeffress, Laura Donohue, Marc Zwillinger, James Orenstein, Mary McCord, Ben Johnson). The report says the FISA courts made the appointments. It does not print which judge signed her designation.
The D.C. district-court bio records James E. Boasberg on FISC from May 2014 and as Presiding Judge from January 2020 to May 2021. The Federal Judicial Center directory records the same FISC years and the same presiding window. April 15, 2021, sits inside that window. Washington Examiner (Jerry Dunleavy, April 29, 2021), Daily Caller News Foundation (April 28, 2021), and the Epoch Times reprint (April 29, 2021) are reporting on the date. A Conservative Treehouse headline that Boasberg “hired” her is commentary. This page does not upgrade that headline into a finding.