The singer celebrated the release of "Expectations" this week by throwing a party at the Warwick in Los Angeles on Thursday, October 25, when she was joined by her pals Normani Kordei and Dinah Jane Hansen.
The trio posed for fun pictures together in a photo booth, which have since surfaced on various fan accounts on social media.
Dinah Jane also shared one of the images taken of herself and Lauren, who donned a feathered black eye mask for the photo booth snap.
"I expect, you expect, we expect," she wrote across the Instagram Story post, as she quoted lyrics from Lauren's track. "congrats to ya bby gal (sic)".
The only member missing from the party was Ally Brooke.
The girl group, which became a foursome following Camila Cabello's exit at the end of 2016, embarked on an indefinite hiatus in May to allow the singers to pursue solo projects.
Lauren is the latest member to share her solo material with fans, and her bandmates aren't the only stars showing their support - Halsey also encouraged her Twitter followers to check out the new music online upon its release on Wednesday.
"Watch the video. Stream the song," Halsey wrote. "Buy the song. Tell your friends. @LaurenJauregui is here and she is not playing around. Expectations. So proud of you baby."
"Lauren is so special because best friend or not, her music would still be exactly what I need in the moment and it gives me goosebumps," she added. "It's just even better that I'm lucky enough to know and love her."
Lauren is so special because best friend or not, her music would still be exactly what I need in the moment and it gives me goosebumps. It’s just even better that I’m lucky enough to know and love her 🖤— h (@halsey) October 24, 2018
The two friends previously teamed up for the track "Strangers", from Halsey's album "Hopeless Fountain Kingdom", while they also recently joined forces on tour.