LoL, guessing a trick from a still picture? There's so many things it could be. Normally I would guess it's most likely an Indy Tantrum or Indy Tantrum to Blind since those seem to be very common Indy tricks. However, after just taking a quick 30-second glance at a video of Nicola's riding it looks very much like it could be her Indy Scarecrow. Just my uneducated guess.
I'd guess indy toeside backroll. the way the water is coming off the toe edge tail of the board +the way her back is makes it seem like she had just gotten the grab and is about to invert.