The 73-year-old, who has played the mother of Tanya Branning since April last year, praised her alter ego's gutsy spirit in an interview with Inside Soap.
"It's surprised me as well that Cora has quite a young following," she declared.
"That's very interesting because people seem to believe there's this great division between young and old people.
"But youngsters respond to her because she's a tough mother and grandmother. They like their strong women too!"
Mitchell played a significant role in Monday's live EastEnders special, with Cora helping to deliver Lola's baby.
Teasing Tanya's discovery that Cora had another daughter, Mitchell added that "many twists and turns" will follow Monday's revelation.
"The whole situation has pierced her thick skin," she added.