Rita Simons, who played Barbara’s on-screen niece Roxy Mitchell, spoke of her devastation at seeing the screen legend’s deterioration.
Speaking to the Daily Star, she said: “From what her husband Scott Mitchell said to me, she has had a real dip lately.
“What I have seen is more confusion, which is really devastating to watch because she always had her marbles together and was always the life and soul of the room.
“It is an incredibly sad thought that my Aunty Peggy, which is what I’ve always called Barbara, isn’t herself.”
Rita added: “From what Scott says there are some dark days but they still have good days, too.”
Barbara’s husband Scott revealed her Alzheimer’s diagnosis last month, admitting she had actually been living with the disease since 2014.
After the news went public, the Peggy Mitchell actress vowed to “carry on” in a recorded message played on ‘Loose Women’.
Her close friend Christopher Biggins also said she had been feeling “pretty low” about her deteriorating health, claiming that she was down about her declining short-term memory.
Barbara was visited by her on-screen son Ross Kemp earlier this week, who praised her braveness.
Visiting my lovely Bar...whoops, I mean Dame Barbara Windsor x pic.twitter.com/dLKvUrhfef— Ross Kemp (@RossKemp) June 18, 2018
Speaking on ‘Good Morning Britain’, he said: “Put it this way, I went round for a cup of tea and I was there for three-and-a-half hours.
“I think what she’s done is very brave, she has a great husband in Scott [Mitchell], he’s been very supportive.
“Honestly, I had five cups of tea, three shortbread biscuits - which is not good for my diet - and I laughed a lot.
“She’s got that great ability, when you walk through the door, she’s ‘on’.”
He added: “It was like seeing my second mum.”