The superstar singer, 29, has quietly been seeing Matthew D. Rutler, a set assistant from her upcoming movie Burlesque – whom she tried to hide from the cameras Friday when they enjoyed a double date at SoHo House in Los Angeles with friends Nicole Richie and Joel Madden.
A friend tells PEOPLE that the relationship with Rutler started as a friendship, then turned into something more.
"It's not serious yet, but it's something she is exploring and finding comfort in," the friend says. "It's new and she’s taking it day by day. She and Jordan were having problems for a long time. What kept them together is their love for their son. She met [Matthew] on set and, during a difficult time, leaned on as a friend. After she and Jordan separated, the friendship turned romantic."
The friend adds that Aguilera's son Max, who'll be 3 in January, is still the singer's No. 1 priority. "Being a great mom to Max is the most important thing in her life," says the friend.
Aguilera makes her acting debut with Cher in Burlesque, a cabaret drama that opens Nov. 24.