If Vi Peacekeeper gets Hidden Bladed in response to her attack trigger, does she stun?

No, Vi, Peacekeeper will not stun an enemy unit if she is killed by Hidden Blade in response to her attack trigger.

Reasoning

1. Triggered Ability Requirement: Vi's ability reads: "When I attack, [Stun] an enemy unit here." The term "here" requires the unit (Vi) to be present at the battlefield when the ability resolves.
2. Interaction with Hidden Blade: When you play Hidden Blade in response to Vi's attack trigger, the Hidden Blade resolves first (LIFO - Last-In, First-Out).
3. Result: Since Hidden Blade kills Vi, she is removed from the battlefield. When the attack trigger subsequently attempts to resolve, it checks for her location ("here") to perform its effect. Because she is no longer at the battlefield, the ability fails to find its source and does not resolve.

This interaction is consistent with RiftJudge FAQ #3820 and FAQ #5667, which clarify that if a unit is removed (killed) from a battlefield before its triggered ability that references "here" can resolve, the ability fails because the unit is no longer present to serve as the reference point.