Does Spirit Rush protect against Power Word Kill?

Question

In a recent session of my game, a point came up where the BBEG cast Power Word Kill on an NPC that the players had given some Spirit Rush to drink within enough time before the encounter. After some deliberation at the table, I ruled that the NPC was dead to keep the game from stalling.

However, after reading the two things multiple times, I am unsure of whether that was actually the right thing.

Spirit Rush:

Inside this elegantly styled bottle is a purple liquid that sparkles. For 1 hour after the imbiber drinks this elixir, anytime she would be reduced to 0 hit points or below, the elixir immediately restores 3d8 + 5 hit points. Additionally, the imbiber becomes ethereal for 1 round and is immediately shunted 30 feet away from the source of the damage. While ethereal, the imbiber can move through walls, objects, or barriers in her path; this movement does not provoke attacks of opportunity. She must end the bonus movement in an unoccupied square. If no such space is available along the trajectory, the elixir heals the imbiber but does not move her away from the source of the damage.

Power Word Kill:

Range: close (25 ft. + 5 ft./2 levels)

You utter a single word of power that instantly kills one creature of your choice, whether the creature can hear the word or not. Any creature that currently has 101 or more hit points is unaffected by power word kill.

Death Attacks:

In most cases, a death attack allows the victim a Fortitude save to avoid the effect, but if the save fails, the character dies instantly.

• Raise dead doesn’t work on someone killed by a death attack or effect.

• Death attacks slay instantly. A victim cannot be made stable and thereby kept alive.

• In case it matters, a dead character, no matter how he died, has hit points equal to or less than his negative Constitution score.

• The spell death ward protects against these attacks.

Reading through these, it seems that the spirit rush would have activated (since power word kill is a death effect, and thus reduces to 0 or less hp) moving the NPC out of range and saving them from the spell. Is this correct?

Edit:

The NPC had a con score of 12, and thus went to -12 HP due to Power Word Kill.

Answer 1

The NPC should have survived this interaction, mechanically. That being said, the rules are awkward enough that a GM ruling opposite is not an abuse of power.

Mechanically

The NPC would be reduced to below 0 hp and the word would acts as an interrupt, so Spirit Rush does activate. They are no longer targettable by Power Word:Kill (either because they were shunted out of range or are now Ethereal, invisible and cannot be affected except by Ethereal creatures and Force effects) and the spell goes off to no effect.

Answer 2

Spirit rush does not protect against Power Word: Kill

Because he is dead long before his hit points are reduced:

Dead

The character’s hit points are reduced to a negative amount equal to his Constitution score, his Constitution drops to 0, or he is killed outright by a spell or effect. The character’s soul leaves his body. Dead characters cannot benefit from normal or magical healing, but they can be restored to life via magic. A dead body decays normally unless magically preserved, but magic that restores a dead character to life also restores the body either to full health or to its condition at the time of death (depending on the spell or device). Either way, resurrected characters need not worry about rigor mortis, decomposition, and other conditions that affect dead bodies.

The wording of the item does not prevent the original effect from killing the inbider, or it would say so as part of it's effect, like the (mythic) spell Deathless (even though that spell also wouldn't help against PW:K), or using (optional) Hero Points.

anytime she would be reduced to 0 hit points or below, the elixir immediately restores 3d8 + 5 hit points.

Reducing his hit points to negatives is a consequence of the creature being dead, and if it's already dead, it cannot receive healing from any source.

Even if you consider that the target has moved away from the spell, that happened after the Instantaneous spell effect was resolved, so it cannot go back on what already happened and change the past. Similarly, you can only get outside of a fireball's area before the spell is cast, or immediately after the spell is cast assuming the effect says you are allowed to escape the area (see Leaping Evasion), but not after the spell already damaged you.