Sarah Michelle Gellar has paid tribute to her Buffy The Vampire Slayer costar Michelle Trachtenberg after she died aged 39.

The veteran actress, 47, took to Instagram on Thursday morning, the day after the news broke that Trachtenberg had pᴀssed away after experiencing poor health following a liver transplant.

Quoting lines from their show, in which the pair played sisters, the star wrote: ‘Michelle, listen to me. Listen. I love you. I will always love you. The hardest thing in this world, is to live in it. I will be brave. I will live… for you.’

Gellar’s pal, fellow actress Jessica Alba, 43, wrote in the comments section: ‘I’m so sorry.’ 

Gellar’s words were accompanied by several images of herself with Trachtenberg. Some were candid while some were from their TV show, and one included the late actress Shannen Doherty, who died of cancer last year at the age of 53. 

Sarah Michelle Gellar has paid tribute to her Buffy The Vampire Slayer costar Michelle Trachtenberg after she died aged 39

The veteran actress took to Instagram on Thursday morning, the day after news broke that Michelle Trachtenberg had pᴀssed after experiencing poor health following a liver transplant

Gellar shared a candid pH๏τo of the two of them being silly, with Trachtenberg having cream on her face

Gellar’s post comes after fellow Buffy star James Marsters paid a heartfelt tribute to Trachtenberg. 

The 62-year-old actor hailed his former costar as ‘very talented’, writing on Instagram: ‘My heart is heavy today. We have lost a beautiful soul.

‘Michelle was fiercely intelligent, howlingly funny, and a very talented person. She died much too young, and leaves behind scores of people who knew and loved her. 

‘My heart goes out to her family who are good people, and are suffering the greatest loss anyone could bear. I hope everyone can give them space to heal in this most difficult time.

‘Godspeed Michelle. You are missed.’ 

Trachtenberg’s Gossip Girl costar Chace Crawford, 39, shared: ‘Michelle was one of a kind. I remember her coming on set for the first time and just absolutely owning it. She was a force of nature and just so so unapologetically funny and magnetic.. remembering those years with a big smile. Just a terrible loss. Love you ❤️.’ 

Meanwhile, Melissa Joan Heart has taken to social media to share a scene that they filmed together for Clarissa Explains It All. 

The 48-year-old actress – who played the lead role on the teen sitcom – wrote: ‘I’m heartbroken to hear of the pᴀssing of @michelletrachtenberg!! So young, so talented and so sweet!

Gellar also shared a pH๏τo of Michelle with Seth Green behind the scenes on Buffy

‘Michelle, listen to me. Listen. I love you. I will always love you. The hardest thing in this world, is to live in it. I will be brave. I will live… for you,’ said Gellar

Trachtenberg, James Marsters, Gellar, Amber Benson, Alyson Hannigan, Anthony Stewart Head, Nicholas Brendon, Emma Caulfield on Buffy The Vampire Slayer 

Read More Inside Michelle Trachtenberg’s tragic final years: Buffy actress, who was a child star and anti-drugs and alcohol campaigner, was ‘struggling’ after liver transplant and links to Hollywood abusers

‘Here is a fun scene from when she was on #ClarissaExplainsItAll. I think this was about 1992 and the episode was an idea I had about babysitting a total nightmare. 

‘But Michelle was nothing like her character and even this young, we got along wonderfully. (sic)’ 

Trachtenberg – who was best known for starring on Buffy the Vampire Slayer and Gossip Girl – was found ᴅᴇᴀᴅ inside her Manhattan apartment on Wednesday. 

The New York Police Department (NYPD) has confirmed to PEOPLE that it responded to a 911 call at 1 Columbus Place in New York City. 

The NYPD added: ‘Upon arrival, officers observed a 39-year-old female unconscious and unresponsive. 

EMS responded to the location and pronounced the victim deceased. Criminality is not suspected.’