I mean, you're going to have people arguing their points as to why this is or is not a tickling pic. But at the end of the day, it's too hard to tell really. The girl next to her is clearly talking to her and laughing as well so perhaps something funny was said? The hands touching her midriff don't appear to be in any type of position or motion where it would appear to cause a ticklish sensation and the spots in which they're touching her don't scream ticklish to me on first glance.
I'm not ruling out the possibility that there was a tickle because it is possible and I believe she is confirmed to be ticklish, but overall it's to hard to tell.
If I had to guess I would say she's probably laughing about something with the girl next to her.