From Jojo’s bizzard adventure (a Japanese manga series written and illustrated by Hirohiko Araki): The answer isn’t clear!
There are several factors that determine what constitutes a requiem stand (stand arrows and Requiem arrows are two completely different items), including what happens to the person the arrow pierces.
In the case of Killer Queen, it is NOT believed to be a requiem stand.
When the user is pierced, the stando does not become requiem. It just gains a new ability.