Inside Kaia Gerber's 21 days of hell since brother Presley's death: Barely eating and disheveled in grief, she emerges after 'mama bear' Cindy pulls her from 'cocoon'... but friends reveal new fears

In the three weeks since her brother Presley died, Kaia Gerber has been holed up at home with her boyfriend by her side, barely eating and in total shock.

But on Sunday afternoon, clad in an all-black ensemble and shades, she was spotted leaving a Los Angeles gym – an attempt at inching back to normalcy at the urging of her mother, Cindy Crawford.

Presley Gerber, 27, died of a suspected overdose after going into cardiac arrest on September 20 while staying at the Santa Monica rehab facility Resolutions Living – a loss that 25-year-old Kaia is understandably still coming to terms with.

'She was in total shock so it was a big emotional process just to come to the realization that she would never see her brother again,' a source close to the family has told the Daily Mail, saying Kaia is 'still struggling.'

After learning of her brother's death, the source said, Kaia – the daughter of supermodel Crawford, 60, and businessman Rande Gerber, 64 – 'stayed at home' with her boyfriend, 33-year-old actor Lewis Pullman. 

'She had a little cocoon there with friends stopping by. She tried her best to hold it together, but she was not eating much, she had no appetite, which is hard for her as she has said in the past she suffers from "disordered eating,"' the source continued, referencing the model's August Vogue interview in which she discussed her 'disordered eating' after entering the spotlight.

'She also has not cut her hair or done her nails, and she has been in sweats the whole time. Her mom has encouraged her to keep a routine going to help deal with grief. That is why Kaia went to the gym.' 

In addition to Pullman, The Shards actress has also leaned on friends and family for support, including the likes of actress Laura Dern and influencer Jake Shane.

'Cindy and Rande have really been there for Kaia, as has George [Clooney],' the source said. 'They are bending over backwards to make sure she is OK.'

But Kaia is also expected to return to work soon. Beyond her 'modeling commitments' she will also star in her next big role alongside Pullman and Dylan O'Brien in the James Morosini written and directed thriller Bulls. According to our source, filming is slated to start by the end of the year, with costume fittings as early as next month.

'It's a good thing her boyfriend Lewis, who is her "rock" these days, is her costar so he can look after her, they are closer than ever,' the insider said.

'The shoot will be on location and will demand a lot of her as she has a title role as a "hedonistic" woman who cheats on her husband [played by Pullman]. Kaia cannot back out, but they can push the dates out a bit.'

'Poor Kaia, this will be hard for her and mama bear Cindy is worried.'

The siblings were extremely close, and in the immediate aftermath of Presley's death, sources told the Daily Mail that 'everyone in the family is worried' about her.

Presley had checked into the Santa Monica facility Resolutions Living the day before he was found dead on September 20.

In footage obtained by TMZ from the night before he died, the model was seen giving a solo tour of the sober home while wearing a white undershirt that showed off his prominent tattoos, a silver chain necklace and a pair of black eyeglasses.

Presley appeared visibly under the influence in the clip, taken around 10pm, as he stared into the camera with noticeably glazed eyes. Throughout the video, he panned the camera around a bedroom and multiple areas of the residence, appearing to be on his own.

Presley reportedly 'got high' on Saturday afternoon and became concerned he was losing control, insiders claimed to TMZ. His sober coach had called the living facility and asked if he could bring Presley in – though he made it clear that Presley was high on drugs – and the facility's admissions officer reportedly agreed, the outlet reported.

The sober coach had reportedly planned to take Presley to a rehab facility the following Monday but needed a temporary hold for the weekend and ended up leaving him at Resolutions Living, according to insiders. Sources also claimed that Presley continued using drugs inside the sober home.

His remains were 'cremated' just days after his passing at the Rose Family Funeral Home, per a death certificate obtained by TMZ. Crawford and Gerber will reportedly keep their son's ashes at their residence.

A final confirmation of any substances that may have played a role in his death must wait until the Medical Examiner's toxicology report is released.

The Daily Mail previously obtained audio of the 911 emergency dispatch call made from the Santa Monica rehab, in which an automated voice could be heard saying 'cardiac arrest' followed by 'overdose.'

The first call was made on Sunday, September 20 at 9.35am regarding a cardiac arrest, however, just three minutes later it was upgraded to an 'overdose,' then finally at 9.40am the priority was upped once again as it was 'upgraded.'

Presley - who started modeling from a young age like his sister - had been open about his decade-long struggle with drug addiction and mental health problems before his death. 

Last November, Presley revealed he had taken a step back from social media to 'take care of my own mental health for a bit.'

One month later, he opened up about his personal life in a candid social media video and started sharing 'Mental Health Mondays' videos on his Instagram. In one, he listed the medication he takes for 'night terrors' and 'panic attacks,' saying his use of medication had been 'fluctuating up and down depending on what's been going on in my life.'

Earlier this year, he posted about having a 'Pre-ibogaine flood dose' at a Mexican treatment clinic, a single, high-dose administration of the naturally occurring psychoactive substance ibogaine that is reported to help with withdrawal symptoms. The high dose is designed to induce a profound 'reset.'

Presley's parents and his sister Kaia praised him for his 'courage' in response to his post about starting the treatment in March.

Crawford commented: 'You are a warrior! Walked thru the fire to find yourself! So proud!' while Kaia added: 'That's my brother I am so damn proud.'

And Kaia wrote: 'I'm so proud of you and your courage. Facing what's hard takes real strength and watching you find your way back to yourself is everything. I love you so much.'

Presley's death came just weeks after Kaia opened up about the enormous toll her brother's struggles had taken on their famous family.

'When something like that happens in a family, it kind of levels everyone,' Kaia told Vogue.

But for all the concerns for Kaia, our source said: 'Kaia has not had it easy in her 25 years, but she will hang in there, she is a very strong person.'

The Daily Mail has reached out to representatives for Kaia and Crawford for comment.

If you or someone you know is struggling with mental health struggles, emotional distress, alcohol or drug use concerns, you can also visit 988lifeline.org. You can also call, text or chat with a counselor by texting 988.