Yes her feet are very ticklish on her soles. In a magazine article it said that one thing that makes her forget about everything is when Blake Shelton tickles her feet.
once on a radio call she talked with a person and he asked does Blake shelton ever tickle you? and she replyed in "well he tickles my feet at times but that's really the only place im ticklish".
Feet are ticklish because they house the nerve endings of your entire lower half, so there is a high concentration of receptors there. The hands and feet are similar in this way, but the hands aren't...