I think mostly the fact that it wasn't set up was what stretched plausibility. My youtube search of Spartacus shield jump found a scene where that maneuver was very much intended by both guys, whereas Nicholas isn't prepared to launch Annalynne. Even though she's light, having a person push their whole weight off a shield while unprepared seems like it could easily mess Nicholas up. Which might be kinda funny and/or dramatic if someone took a hit because of it. The jump would also be really tough to pull off, as Nicholas's shield is probably moving, considering that he's in the middle of a fight.
Just my two cents. I thought the post was fine otherwise.
@IcePezz I do agree with Luminosity. Literally the only reason for Nicholas to hold the shield up horizontally in a way that would allow Annalynne to jump off of it would be if there was a weapon coming at him or Fiona in an overhead attack, which would then be bound to hit Annalynne. Not to mention that doing something like that without the other person being prepared or at least aware could seriously disrupt their balance.
Personally, I feel that it's really pushing it but as long as icmasticc is fine with it, I won't say anything.
That said, should Nicholas or Fiona suffer an injury in this round, he will blame Annalynne for it. :P