The Jolene singer, 68, said her upbringing in a two-room wood cabin in rural Tennessee meant she would have no qualms wading through the mire to an outside toilet, like other festival-goers.
She also told of her excitement that Led Zeppelin frontman Robert Plant would be at the festival when she follows in the footsteps of James Brown, Shirley Bassey and her friend Kenny Rogers to fill the early-evening Sunday legends' slot.
After being shown snaps of the Somerset event's habitual mud bath, she said: "I am going to be wearing my high heels, but I just may stay in my bus until I have to get on stage."
But she went on to say: "That's how I grew up. If I'm tramping to the toilet through mud, that's no big deal for me."