Well, she might still need some practice. But I gave her some good training, and tested it out a few times, and I think she got it. Here's how we went about it...
1) She flinches and draws back when someone looks like they are going to tickle her. She anticipates the discomfort and what her usual reaction is, and already feels ticklish before she's even been touched. I told her to practice relaxing, and just watching the person who might tickle her. They aren't yet, and so what if they do? Don't flinch until you're forced to.
2) We got her to see tickling for what it is. Just skin on skin. I "tickled" her feet and told her to focus on diminishing her instinct to kick my hand away and laugh. We conditioned her to feel a different sensation. There's no switch I was flipping to demand that she react, and she could control how she reacted if she thought about it the right way.
3) Like I touched on briefly in 1 & 2, I stressed again to her that tickling is mostly a mental game. There will be some situations where you cannot help but feel tickled, and you'll have to react if you can't get away. We both knew that. Certain people have a knack for getting you good. But look, that hand coming toward you? It's just a hand. Will it touch your side? Maybe. But you can defend yourself. Flex your muscles, that helps. But mentally relax. You'll make it through unscathed.
I kept thinking about this later. I thought about how what I told her really boiled down to...
Don't be anxious.
Put it in perspective.
Be strong, be capable, but be relaxed.
This has happened to me before... maybe to you... when you realize the advice you've just given is of the kind you could use yourself.
"As a single footstep will not make a path on the earth, so a single thought will not make a pathway in the mind. To make a deep physical path, we walk again and again. To make a deep mental path, we must think over and over the kind of thoughts we wish to dominate our lives."
-Henry David Thoreau