January 12, 2017 2:26 PM EST

One week after the joint memorial service for Carrie Fisher and Debbie Reynolds, Billie Lourd has taken to Instagram to remember her mother with a throwback picture.

The Scream Queens actor shared a childhood photo of herself sitting in the backseat of a car with Fisher, accompanied by a heartfelt caption. “If my life weren’t funny then it would just be true and that is unacceptable,” she quoted her mom, adding, “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.”

Fisher and her Lourd’s grandmother, Reynolds, passed away within one day of each other in late December. See the full tribute below.

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Write to Megan McCluskey at megan.mccluskey@time.com.

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