They aren't technically tickling her, just extracting salt from her sweat. The innocent intention doesn't help the reality though. Poor Mrs. Hudson, her armpits and inner thighs are her weak spots, too.
I've literally never done this before because I didn't know how BUT my Patreon is currently 25% off if you use the code BLKFRI 💙 GO FORTH AND FILL THINE EARS WITH HORNY AUDIOS