Selena Gomez Canceled Festival Performance, But BFF Demi Will Take Her Place

Speculate wildly about the ups and downs of Selena Gomez and Demi Lovato's friendship if you'd like — I can't stop you and, more importantly, I won't stop you — but Demi is stepping up in a major way for her former “Barney & Friends” co-star.

Selena, who spent the summer traveling for her Revival World Tour, recently announced she'd be taking some time off to tend to her personal well-being.

She told PEOPLE,

As many of you know, around a year ago I revealed that I have lupus, an illness that can affect people in different ways. I've discovered that anxiety, panic attacks and depression can be side effects of lupus, which can present their own challenges. I want to be proactive and focus on maintaining my health and happiness and have decided that the best way forward is to take some time off.

Time off means the 24-year-old will be unable to appear at the Global Citizen Festival's fifth annual advocacy show September 24 in New York's Central Park, PEOPLE reports.

Demi graciously joined the lineup, which includes Rihanna, Kendrick Lamar, Metallica, Usher, Chris Martin and Ellie Goulding, to cover for her BFF in need.

The pop star said,

The Global Citizen Festival combines music and activism in a way that inspires and affects millions around the world. I am proud to support this amazing organization's ongoing efforts to improve global healthcare and to end extreme poverty.

The festival is thrilled to have Demi on the roster, as well.

Global Citizens founder and CEO Hugh Evans stated,

Demi has been an incredible ambassador for global health and gender equality campaigns for many years. We are so thrilled to align her artistry and advocacy and have her join us as a headliner...

As Selena recuperates, she can watch along at home on MSNBC, MSNBC.com or YouTube beginning at 3 pm EST the day of the festival.

Citations: Demi Lovato Joins 2016 Global Citizen Festival Lineup as Headliner (PEOPLE)