"It was beautiful. I thought everyone did such a beautiful job. It was so gorgeous. I loved how [Ariana] ended it. I thought Justin did great. It was really beautiful," she gushed.
Bieber, Grande, Miley Cyrus, Chris Martin and other stars performed Sunday to honor and raise funds for the victims of the recent Manchester attack. 22 people were killed in a bombing May 22 at Grande's concert.
"I'm not going to let go of hope. I'm not going to let go of love. I'm not going to let go of God," Bieber, who sang acoustic versions of "Love Yourself" and "Cold Water," told the audience, according to Us Weekly.
"God is good in the midst of the darkness. God is goos in the midst of the veil. God is in the midst no matter what's happening in the world. God is in the midst and he loves you and he's here for you," he added while holding back tears.
Gomez and Bieber split in 2014 after several years of on-again, off-again dating. The actress has since started seeing singer The Weeknd, born Abel Tesfaye.
"She is head over heels in love with Abel," a source told E! News last week. "This relationship is very different than the one she had with Bieber."
"She has really found who she is and what makes her happy," the insider added. "They have gotten to know each other very well and have learned from their past relationships what they want and don't want."