Hey, all...
When it comes to either tickling or relationships, I'd be lying if I said I had a whole lot of credentials and expertise, but let me offer a thought.
In surfing the Yahoo groups, trying out key words just to see what came up, I learned that there is such a thing (with far fewer members than the tickling groups, to be sure) as a fart fetish. That's right, there are people who get turned on by having their partners pass gas in their faces.
I didn't probe for details, and truth be told there wasn't a whole lot to be found under this category, but I would guess that somewhere out there, there's somebody who is so totally into this fart fetish as to think that those who don't share the enthusiasm just haven't had the right opportunities and exposures, and don't know what they're missing.
Closer to home, I know from my own circles in another quirk of mine--nudism--that there are many nudists who think that those who aren't nudists just have a silly hang-up about their bodies, or about the need for clothing, that can and should be overcome with the right persuasion.
Point is, whatever you're into, you do have to know, not everybody will share it. I would say, when it comes to your girlfriend who hates being tickled, don't count on ever getting her to let you tie her up and tickle her. (For Pete's sake, don't take Psyco's advice; that advice is, well, "psyco.") Chances are, the most you can realistically hope for is a little casual tickling here and there. Next question, can you live with that, or do you need a systematic ticklee for a partner? (I use systematic as opposed to casual.) If you remain bonded to this one, will she be cool with your having a group of friends with whom you get together to tickle? In other words, can you accept that she's not into it, and can she accept that you are? I'm not expressing an opinion on how either of you should answer these questions, but I do think these may be the real questions.
Of course, if it turns out that she really does want to be tied down and tickled till she feels like she's being electrocuted, then let the party begin; I only say, don't count on it, and have a Plan B.