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.