"She had been feeling a little poorly and had gone in for some tests," Sonia Hearld told The Mirror.
Jean returned to her care home but had to return to hospital on Tuesday.
Despite her 23 years playing Hilda on Coronation Street, the actress admitted she no longer tuned into the soap because the story lines no longer interested her.
She complained that there was so much focus on sex that she eventually lost interest.
Speaking to The Daily Express, Jean said: "The only stories they seem to have in mind is who's jumping into whose bed next. I lost interest somehow."
She admitted that while she understood that the show had to move on, she longed for the days when the street was gentle, funny and human.
Jean felt the humour had all but gone out of the soap.
Jean, who lived in Southport, also explained that she would not return to Coronation Street after bowing out following the death of her on-screen husband Stan.
She said: "It is more than 25 years since she [Hilda] left the Street and I have been asked a number of times to do an episode but she wouldn't be the 'old scrubber' she was, now.
"Hilda had a bit of sense in her head; she would have adapted, smartened herself up and learned to speak better."
She added: "People would want her to be the old Hilda. I couldn't do that."
Jean suffered several health scares in her final years.
In June 2014, she was taken to hospital by ambulance. In the same year, she suffered a slight stroke.
After her death, fans of the show sent Jean hundreds of condolence cards.
