The photograph featured the two sitting in what appears to be the back of the car at a time when Lourd, 24, was much younger. Mother and daughter were smiling at the camera and leaning toward each other.
“‘If my life weren’t funny then it would just be true and that is unacceptable,'” she wrote, quoting her mother.
She continued with her own words, writing, “Finding the funny might take a while but I learned from the best and her voice will forever be in my head and in my heart.”
Lourd’s post comes just weeks after her her mother and grandmother, legendary actress Debbie Reynolds, both passed away just one day apart. She received an outpouring of support, notably from many of her Scream Queens costars, including Taylor Lautner, who she was seen with on Monday in Los Angeles.
A source told PEOPLE Lautner was “a great guy and has really been there for Billie.”
The actress has largely kept away from social media, other than to thank everyone for their well-wishes and prayers. Fisher, 60, was aboard an 11-hour flight from London to Los Angeles on Friday, Dec. 23, when she went into cardiac arrest. Paramedics removed her from the flight and rushed her to a nearby hospital, where she died on Dec. 27. Just one day later, on Dec. 28, Reynolds was rushed to the hospital due to a possible stroke. She died at the age of 84.