In a Facebook posting, Collins claimed "a close mutual friend" said Mitchell "is walking, talking, painting some, doing much rehab every day".
Folk singer Mitchell has been undergoing treatment since she was found unconscious in her home in March.
She is known for songs like Big Yellow Taxi and Case of You.
"I have another friend who went through something similar," Collins' post continued.
"It does take a long time, three years for my friend, who has really totally recovered professionally and personally. I will try my best to see our songbird when I am in LA in the coming weeks."
In June, singer David Crosby - who dated Mitchell in 1967 - said she was not speaking.
He told the Huffington Post: "She took a terrible hit," he said. "She had an aneurysm, and nobody found her for a while. And she's going to have to struggle back from it the way you struggle back from a traumatic brain injury."
However, her lawyer Rebecca J Thyne, who visited Mitchell at her Los Angeles home contradicted that assessment saying: "It was clear that she was happy to be home and that she has made remarkable progress.
"She has physical therapy each day and is expected to make a full recovery."
Mitchell's friend Leslie Morris, has been acting as her temporary conservator.
Tyne has recommended that she remain under a conservatorship until Mitchell fully improves.

The boy was found "safe" this afternoon and arrested on suspicion of wounding and carrying a bladed weapon.
Police said he was found on a train from Hereford to Malvern at 16:55 BST.
Detectives launched a search for the boy after the attack at Chase Technology College in Malvern, Worcestershire, at about 08:45 BST.
A male teacher and 13-year-old girl suffered minor injuries.
The boy was apprehended at Ledbury station in Herefordshire.
Leah Johnson, 16, a former pupil of Chase College, was travelling on the train when it stopped at Ledbury.
She said an officer was waiting on the platform for the boy, who had been standing near the train doors for around 15 minutes.
"The policeman was pacing up and down. The doors opened and he just said 'can you come with me?' and he walked off with him," she said.
The boy remains in custody at Worcester Police Station.
Earlier, there were police officers stationed at each entrance to the school and crime scene tape blocking off the main entrance.
Children were brought out individually from the school and handed to parents waiting at the gates. About 100 had gathered by lunchtime.

North Cumbria University Hospitals Trust said it was discovered over a week ago by a member of staff who alerted senior clinicians.
It said there was "no indication that any patients have been adversely affected".
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Singer Joni Mitchell is recovering from a stroke and brain aneurysm earlier this year, her friend and fellow singer Judy Collins has said.
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A 13-year-old schoolboy who disappeared after a fellow pupil and a teacher were attacked with a knife has been arrested, West Mercia Police said.
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