EXCLUSIVE: Dolly Parton's 'Driving Herself to the Brink of Death' with 'Brutal' Work Schedule — 'She's Working Herself Into an Early Grave for Her Fans'

Dolly Parton is feared to be "driving herself to the brink of death" with a "brutal" work ethic, sources are warning RadarOnline.com.

Despite mounting health fears for the 79-year-old and the toll of her ongoing grief over the recent death of her husband Carl Dean, she is keeping up a relentless pace from her sickbed for the sake of her fans.

The country legend was forced into cancelling concerts this year – including a planned Las Vegas residency – after a series of medical setbacks left her recovering at home in Brentwood, Tennessee, where she had lived with her long-term love Dean for nearly six decades until his death in March.

Though doctors instructed her to rest following a severe infection caused by kidney stones, Parton has struggled to slow down, insiders say.

"Dolly's body may be down, but what truly bothers her is being forced to stop working," a longtime family source said.

"She's in mourning, she's restless, and she's desperate to dive back into the work that keeps her grounded."

Another insider close to the singer added: "She goes to her ranch seeking peace, but the quiet wears on her. Keeping busy has always been how she gets through things. If she doesn't ease up, she's only speeding up her decline. What she's doing is essentially working herself into the ground."

Despite her weakened state, Parton has resumed tending to her sprawling business empire, estimated at $650 million, including her Dollywood resort and merchandise lines such as her designer jeans collection.

Her recent social media post – "New season, new styles ... Dolly's Joleans are back and better than ever" – signaled to friends and fans she was already re-entering the work fray despite medical advice to totally rest.

Those who have watched her push through grief and illness say her pattern is all too familiar.

Parton has admitted in an interview to promote her latest memoir she had been running herself into the ground even before falling ill.

And while she tried to reassure fans by declaring "I ain't dead yet," those close to her say the sentiment masked deeper fear.

"She has no concept of taking it easy," one family source said. "The thought of not constantly producing something scares her."

From her bed, Parton has remained heavily involved in Dollywood's operations, phoning senior staff daily and participating in staffing decisions.

She has also insisted on personally checking in on older friends she worries may be struggling.

"That's just always been her way, no matter what her personal circumstances are," a source said. "She's built to look after everyone around her, but the trouble is she's now seriously neglecting her own well-being."

Those inside her circle describe a woman torn between physical frailty and lifelong instinct. "She's always pushed non-stop," one source added. "But the fear now is that she's pushing even harder right when her body is begging her to slow down."