When the person doesn't tell you they don't want you to do it - ever - then you shouldn't do it. However, my husband and adult kids and I engage in a little bit of playful teasing, which is sometimes physical. For instance, I might tap my son on top of his head from behind. He'll reach up as I move my arm. This gets repeated till he catches me (whereupon he'll tickle me or simply immobile that arm for a few minutes) or it seems like he's fed up with it. Likewwise, my husband will tickle me once in awhile, but usually on my neck or my leg, because I have told him I don't like to be tickled on my torso. If he discontinued this, after awhile I'd probably wonder why he had stopped.

I suspect Zarasophist's tickling is more along those lines. Pinning her down and preventing her from defending herself on a daily basis is just twisted.