The 15-year-old Beer is the product of a few well-timed tweets by Bieber, who sent his Beliebers a link to check out her music back when she was only 13. She signed a record deal with Island Def Jam and is currently managed by (who else?) Scooter Braun.
Madison's mother actually revealed the reunion via Instagram. She posted a photo of Madison and Justin in the studio, then followed it up with a photo of Madison and Selena in the same location.
TMZ later posted a video of Justin welcoming Selena to the studio.
Madison's latest single Melodies has almost 5 million hits on YouTube. She's working to release her debut album sometime in 2014.