Reynolds was born on April 1, 1932, but sadly, the Singin' in the Rain actress didn't reach the 85 year milestone. Instead, she died last December just a day after her daughter Fisher in a Hollywood shocker.
Lourd, 24, captioned a photo of Reynolds wearing a green sweater and pants with Fisher standing behind her, "Happy 85th to my constantly classily clad Abadaba."
As Radar has reported, Reynolds died at age 84 on Dec. 28, just one day after her "Star Wars" actress daughter Fisher passed away at age 60. Fisher had been rushed to a Los Angeles hospital after having a heart attack on an airplane coming home from London.
Carrie's brother, Todd Fisher, has said his niece Lourd is "genetically Carrie and Debbie" and that her father, CAA agent Bryan Lourd, has been her rock: "He has supported her beautifully."
Todd told ET of Billie, "She is a lot more like my mother even than Carrie."
Lourd raised eyebrows by wearing a bikini in Cabo while on a getaway with boyfriend Taylor Lautner not long after Fisher and Reynolds' deaths, as Radar has reported.
But fans understand the pressure young Lourd has been under as she copes with the deaths of her both her famous mom and grandma.
Last weekend, fans honored both Reynolds and Fisher's storied lives in an emotional public memorial in which Fisher's former fiancé Dan Aykroyd paid tribute.
And with her April 1 Instagram reminder, Lourd is making sure Reynolds and Fisher are never forgotten.
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