Billie Lourd pays tribute to her late mom Carrie Fisher on her birthday

Carrie Fisher's daughter, Billie Lourd, is keeping her late mother's spirit alive on the actress' birthday.

Lourd shared a video on Instagram Monday, in which she sings Tom Petty's "American Girl," saying the song was her mother's favorite.

Fisher, who died of cardiac arrest on December 2016, would have been 63 today.

"Not that I’m some kind of grief expert by any means, but on milestones (or whatever you want to call them) like this, I like to celebrate her by doing things that she loved to do. So here’s a little video of me singing one of her favorite songs (American girl by Tom petty) in one of her favorite places (her bathtub, of course)," Lourd wrote. "I’ll probably have a pint of vanilla Haggen Dazs and a Coca Cola for dinner."

Lourd, 27, whose father is Fisher's former partner, talent agent Bryan Lourd, has honored her mother several times since Fisher's death. Last December, she shared a video of herself singing Jackson Browne's "These Days," along with a note explaining how "vulnerable" it made her feel. Singing with Fisher, whom she called "Momby," was a favorite past time.

"I’ve found that what keeps me moving is doing things that make me happy, working hard on the things that I’m passionate about and surrounding myself with people I love and making them smile," she wrote. "I hope this encourages anyone feeling a little low or lost to 'keep on moving.' As my Momby once said, 'Take your broken heart and turn it into art; - whatever that art may be for you."