Well, let's see. There's "I like tickling," and there's "I get off on tickling and in fact I belong to this big worldwide cyber community where people order videos of people getting tied and tickled, post stories about it, and have conventions where people come from miles away to get together and tie each other up on bondage equipment and tickle each other." And there are gradations in between. But actually, you are in a little bit of a danger zone, because doing something that seemed funny and playful to her, and then telling her that what you did was a sexual act for you--that may or may not go over well. The thing that I come back to is, when you have a question of whether it's appropriate to tell someone about your tickling fetish (or whatever else you prefer to call it), the answer generally involves considering whether your relationship with this person is conducive to talking about your sex life and your sexuality in general, because essentially what it is. It's not like telling her that you're into rock climbing or stamp collecting.
And as for the question, I don't know how else you describe it other than to say you like tickling, lol
