I don't know if Bettie ever did tickling related material but Irving Klaw was supposed to have done a good bit of it during his heyday. I read somewhere years ago that when Klaw destroyed the bulk of his work after the government began its investigation of him, his racier photo negatives, including those of bound women tickled at the hands of other female models, were among the items he burned. I think Klaw's lawyer advised him that they would be considered pornographic and his collection was lost. Certainly there must be some of it in existence in private hands and hopefully those who have it will one day make it available.