I have three answers for this.
The most ticklish woman I know was my wife's boss who I have not tickled but my wife tickled her in front of me and two strokes almost made her fall off the couch.
I have tickled quite a few females but I did not tickle most of them for long periods. I have two who I tickled a stoke here and there many many times. One is my neice who I actually do not touch anymore (she changed a lot nothing to do with age or anything both girls were of age) who has a very very ticklish arch stay in the arch and she would beg for me to stop. The other was a coworker when I was much younger. She would pop her shoes off at work and sit on one ankle knowing full well as soon as I passed her my fingers would find her foot. She would burst into giggles as my fingers went the length of her foot and tell me to stop all the while grinning.She would even wiggle her toes when she knew I was behind her. I think she thought it would help her since I was technically her boss there was no real attraction to me.
Just off the top of my head, I'd have to say my friend S___________. She is one of those people who I could never ever convince to go for tied-up tickling. She really freaks out. I mean totally...scary...bonkers...hyper-sensitive.
My ler has INSANELY ticklish feet...sometimes she'll let me tickle them, as long as I promise to do it lightly...sometimes though, I can't resist...😉 She has a loud, incredible laugh...