Billie Lourd Shares Throwback Photo of Mom Carrie Fisher

Lourd is mourning the loss of her mother and grandmother, Debbie Reynolds.

On Wednesday, the 24-year-old actress shared on Instagram a touching throwback photo of her with her mother. In the picture, the pair are seen embracing while seated in the back of a car and smiling at the camera.

"'If my life weren’t funny then it would just be true and that is unacceptable,'" she wrote, quoting her mother.

"Finding the funny might take a while," Lourd continued, "but I learned from the best and her voice will forever be in my head and in my heart."

Fisher, 60, died on Dec. 27, after going into cardiac arrest on a flight from London to Los Angeles four days earlier. Reynolds, 84, passed away a day later after suffering a stroke while making funeral arrangements for her daughter.

Last week, mother and daughter were laid to rest at Forest Lawn Memorial Park in the Hollywood Hills, a day after they were honored at a private memorial service. Reynolds was buried along with some of her daughter's ashes in a pill-shaped urn, Ruta Lee, a friend of the "Singin' in the Rain" actress, told ABC News.

Lourd, a star of "Scream Queens," thanked her fans during that difficult week.

"Receiving all of your prayers and kind words over the past week has given me strength during a time I thought strength could not exist," she wrote on Instagram. "There are no words to express how much I will miss my Abadaba and my one and only Momby. Your love and support means the world to me."