Billie Lourd Wishes Late Grandmother Debbie Reynolds Happy Birthday

Billie Lourd has paid tribute to her grandmother, actress Debbie Reynolds, on what would have been her 87th birthday.

The 26-year-old actress posted a sweet throwback photo on Monday featuring her late mother, and Reynolds' daughter, Carrie Fisher.

The picture shows all three smiling for the camera as Reynolds sits in what looks like a makeup chair.

“Happy birthday abadaba,” Lourd wrote all in emojis, calling her by the nickname she has for her grandma.

READ MORE: Billie Lourd Performs Moving Tribute To Mum Carrie Fisher

Lourd tragically lost both her mother and grandmother within a day of one another in December 2016, when Reynolds suffered a stroke one day after Fisher died of a heart attack at the age of 60.

In 2017, Lourd spoke to Ellen DeGeneres about the hardships of adjusting to life without both her mum and grandmother.

READ MORE: Billie Lourd Says American Horror Story 'Saved My Life'

“It’s completely surreal,” she said.

“There’s no way to really explain it -- it’s so hard to talk about. If I say I’m doing good, I’m too happy. If I say I’m not doing good, then I’m a mess. So it’s really hard to know what to say about it because it’s so surreal and impossible to deal with.”

One method of coping with her huge loss, Lourd told Town & Country, is remembering her mother’s wicked sense of humour.

“If life’s not funny, then it’s just true -- and that would be unacceptable,” Lourd said.

“Even when she [Fisher] died, that was what got me through that whole thing. When Debbie died the next day, I could just picture her saying, ‘Well, she’s upstaging me once again, of course -- she had to'.”

Following her mother's death, toxicology reports showed that Fisher had drugs present in her system, prompting Lourd to address her mum's battle with drug addiction and mental illness.

“Tons of people grow up with mentally ill parents who have drug problems… It’s such a common thing, and people really don’t talk about it, ” Lourd said to PEOPLE.

“It ultimately helped so many more people.”