Just another $0.02 from the Professor:
While some people do get less ticklish bc they have been tickled by you before, that is unusual (have only seen it once). Here are some thoughts:
Buy her a pedicure at a local spa - regularly and be patient. Even if this does not work right away she will still love you for it and her feet will look great!
Even out the play if she wants to: ask her if she would like to be the tickler some time and tickle you.
Hot wax treatments for the feet increase sensitivity
Bath and Body works has these blue socks and gloves for softening the hands and feet which work VERY well especially when combine with the lotion from the same line. I reccomend them - they are a few $$$ but as they say you get what you pay for!
Find out what SHE likes. Do the romantic things for her she likes (if you are not sure, feel free to PM me for some ideas). If you focus on satisfying her every need then she is free to focus on meeting yours. If you do this, wholeheartedly and selflessy for a couple of months and she ignores your needs - dump her and find someone who will. That is a HUGE indicator of the success potential of your relationship as a whole. You may very well see her suddenly taking an interest in fulfilling your every tickling fantasy to make you happy and keep you! 😀
I also agree with the advice above in the thread, varying your technique, etc.
To really be a ticklish lee, she needs to trust you completely and have total security in you and your relationship. She hopefully is already there, but ask her anyway and address anything that comes up. Make sure that when you are tickling her you are focusing on not just tickling but tickling HER. If the focus is on the tickling and not on her, she may feel a bit lost and maybe even a little used.
One thing one needs to understand about the female human is that she is commonly a creature of mood. Foreplay is crucial. If you make tickling an erotic part of your relationship (link it with her sensual and sexual pleasure - yes these are different, especially for women) she may very well come to see the pleasure in it that you find and actually with time come to crave it as you do. The result when this takes place is the most blissful intimacy you have ever imagined and then some. Incorporate the tickling element into the small little foreplays all day long and over days of time that it commonly takes to put a woman into "the mood". (For best results time this for ten days to two weeks after the start of her menstrual cycle). Make sure that tickling is not the main focus of your efforts, but rather that pleasuring HER is. She needs to know that this is not with a goal of sex or an act of tickling in mind, but rather for the purpose of pleasuring her in and of itself for its own sake (which means you have no expectations). When she eventually craves more physical intimacy and ends up recieving the most phenomenal orgasm of her life amidst being tickled silly, her view of tickling and her desire for it (and therefore her ticklishness) will likely increase. Sounds counterintuitve to most guys but women are like flowers: you cannot force the petals open, you must patiently nuture them, take care of them, and give them what they like and with time you will be shown a beauty you never expected. When that happens, care for that flower all the more and it will continue to bloom.
Good luck and best wishes,
Professor TKL