Cedric and the Priori Incantatum *Corrected and Updated*

One of the most important and anticipated scenes in the Harry Potter series happens in Harry Potter and the Goblet of Fire when Voldemort gets his body back and fights Harry once more.

We're all wrapped up into the story, after all, Voldemort is back alive and well in a new body. Furthermore, Harry has to duel Voldemort to escape. In doing so, Priori Incantatum came into effect, thus giving Harry enough time to take Cedric's body and the Triwizard Cup back to Hogwarts.

It's a very powerful and important scene and the movie brings Rowling's words to life perfectly. 

So all should be fine, right?

Yeah . . . no.

Does anyone else see the problem with this scene? 

Bear in mind, I am not referring to the bloop appearing in the first edition of the book where James appears first instead of Lily, opening a plot hole because James died first.

Still don't know what the problem is?

Lets look at the shades/ghost-like people coming out of Voldemort's wand during the Priori Incantatum. Cedric Diggory, Frank Bryce, Bertha Jorkins, Lily Potter, and finally James Potter.
     BUT   one of these things is not like the other.

While Cedric died in the graveyard, Voldemort didn't kill him; Wormtail did. So, unless Wormtail was using Voldemort's wand at the time, Cedric should never have appeared from Voldemort's wand.

The only thing to do is to ask why. Perhaps Cedric appeared only to ask Harry to take his body back to his father? 
     But if that's the case, Rowling could have written that Harry grabbed Cedric's body and used the portkey -- it fits well within his personality, especially given the Second Task where he waited to make sure that everyone was rescued.

So why? Why did Rowling choose to write the scene the way it is when it could be confusing as to who killed Cedric Diggory?

Thoughts, anyone?  



A friend pointed out the error I made in this post and I apologize for any confusion that caused. 

Anyhow, she did make a point. Wormtail could have been using Voldemort's wand when he killed Cedric, thus tying up this problematic plot hole.