i have a friend that used to have really ticklish feet. me and some of my other friends would always have tickle fights with her and her feet, especially her toes were always the best spots to go for. however, just a few days ago everytime we'd go for surprise attacks on her feet, she said that it doesnt tickle as much as it did before. now it's to the point where she's not even ticklish there anymore? is there any way for her to regain her ticklishness on her feet again?