"A" looks to me to be the sort who will either find it too much to take and will dissolve into tears and hate you forever, or she would interpret it as a lovely gentle sensuous emotional experience, which is some people's tickling style, but is not really mine. She looks heart-meltingly lovable, but perhaps not for tickling.
"B" looks like she might possibly turn out to be wearing so much defensive psychological armour that she would not let herself get tickled, and might even have convinced herself that she isn't ticklish, but on the other hand if she does turn out to be very ticklish then, my god, she is the one that would be my biggest turn-on to tickle.
Thanks for giving us such an enjoyable conundrum to solve; that was a nice way to spend five minutes.