The first way to approach this is as a GRV. Technically speaking, Nissa is responsible for giving Ajani priority before resolving the trigger, which means in this case she’s violated the CR. We can assess the GRV for the error, but a rewind is impossible here and no partial fixes are relevant.

The second approach is to look at Nissa’s actions as a proposed shortcut. While she didn’t communicate it well (or at all), what she’s doing is shortcutting through two priority passes straight to the trigger resolving. Shortcuts exist to allow players to just play, and not worry about the highly technical side of things, so in many situations this would be fine. Unfortunately she didn’t give him the chance to accept or reject her shortcut, which violates the MTR in a way that’s not a specific infraction. As such, there is no penalty, we would simply tell her that she needs to not repeat this error, and any further issues of this type would be handled with USC-Minor and an investigation.

Both approaches lead us to the same place- the game has been messed up in a way we don’t have the power to fix, we tell Nissa she needs to be more careful moving forward.