Failed presidential candidate Hillary Clinton has reportedly backed out of Fortune’s Most Powerful Women Summit featuring 2020 presidential candidate Rep. Tulsi Gabbard (D-HI) and former Department of Homeland Security (DHS) Secretary Kirstjen Nielsen.

Clinton and Nielsen were both slated to deliver a speech at the event in Washington, D.C., but the former first lady canceled her planned appearance because of scheduling issues, her team claimed.

Slate reports:

[A] person close to Clinton’s decision-making process told Slate that she had decided to drop out after hearing that Nielsen was also on the docket. “We work with a lot of activists who are trying to do their best to improve this horrible situation down at the border,” the person said, citing Clinton’s support of RAICES and other organizations that advocate for asylees and immigrants. “At the end of the day, it’s an easy decision. You have to side with them.” The person said one of those activists alerted Clinton to Nielsen’s slot on the schedule earlier this week, after which Clinton’s team notified Fortune that she would no longer be attending the event. Friday evening, Clinton’s name and headshot were removed from the summit’s website.

Nielsen’s inclusion in the event has garnered blowback, resulting in over 51,000 people signing a petition demanding Fortune boot the former Trump cabinet member from the event. However, Fortune communications manager Alison Klooster signaled there are no plans to bow to the pressure campaign:

Fortune strongly believes that interviewing Nielsen—and other key figures from the private and public sector, however controversial—is important journalism and provides us an opportunity to ask substantive questions in front of our viewers and readers.

Nielsen served as head of the DHS from December 6th, 2017 to April 10th, 2019. The event will take place over October 21st-23rd.

In addition to Nielsen, 2020 presidential candidate Rep. Tulsi Gabbard (D-HI) — whom Clinton attacked on Friday as “the favorite of the Russians” — is also scheduled to attend the Fortune event. Appearing on a podcast hosted by David Plouffe, President Barack Obama’s 2008 presidential campaign manager, Clinton claimed Gabbard was being “groomed” by the Kremlin as a potential third-party candidate.

Gabbard clapped back at Clinton in a series of tweets, branding her the “queen of warmongers” and the culprit behind a smear piece published by the New York Times ahead of this week’s Democrat presidential debate in Westerville, Ohio:

Great! Thank you @HillaryClinton. You, the queen of warmongers, embodiment of corruption, and personification of the rot that has sickened the Democratic Party for so long, have finally come out from behind the curtain. From the day I announced my candidacy, there has been a … — Tulsi Gabbard (@TulsiGabbard) October 18, 2019