The actress, who played Jo Grant in the BBC sci-fi drama between 1971 and 1973, suggested that her Doctor Who co-star Jon Pertwee would be "very proud" of his successor.
Asked if she is still a fan of the show, Manning replied: "Ever since Christopher Eccleston came out of that goddamn box I've loved it. All the new Doctors are brilliant.
"It's an education to watch [Matt's] beautifully realised physicality as the Doctor. I said to him, 'Jon Pertwee would be very proud of what you're doing with this character'."
Manning added that she thought Russell T Davies "absolutely nailed" her character in a 2010 episode of The Sarah Jane Adventures, which saw her star alongside Smith and the late Elisabeth Sladen.
"It was the first time I'd actually worked with Lis, although we'd already become close friends," she explained to the Radio Times. "We had a lot of past with Jon that bonded us.
"When I was a newbie at conventions, she really helped me through. After she died, I said in an interview she was the quintessential Doctor Who girl. And I really meant it."
Jenna-Louise Coleman was announced as the latest Doctor Who companion in March, replacing Smith's current colleague Karen Gillan.