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.
Singer Joni Mitchell is recovering from a stroke and brain aneurysm earlier this year, her friend and fellow singer Judy Collins has said.