The first photo captured the newly 21-year-old donning a Mrs. Claus-inspired red and white off-the-shoulder dress complete with white fluffy trim and elbow-high red velvet gloves to match her ensemble. She accessorized with candy-cane hoop earrings and wore a bold eye-makeup look. Other photos in the carousel featured Eilish in a photo booth with her boyfriend, 31-year-old Jesse Rutherford, who is the lead vocalist of The Neighbourhood, along with Justin Bieber and his wife Hailey Bieber. Eilish and her boyfriend also posed in front of balloons that spelled out “Happy 21st Birthday” as they posed with their hands behind their backs while they faced each other, leaning in and smiling wide at one another. The singer captioned the carousel of photos with red heart emojis covered in fire flames and presents. Hailey commented on the post with a red heart emoji and heart eyes. Fans were also completely smitten to see Eilish, Rutherford, and the Biebers all in one snap as the 21-year-old is a longtime fan of Justin and is now one of his close friends. Younger Eilish would be squealing right now!“I can’t even begin imagining how young Billie would be shaking if she would know that u would find yourself in the same photo booth as JUSTIN AND HAILEY AND JESSE” one fan wrote. “The young Billie…. Can’t believe that Justin Bieber is at her own party right now!” another fan commented.We’re wishing the singer the happiest of birthdays and we hope this is the best year yet!