"She would have been 22 next week"?
If she were/was alive, she would have been 22 next week.

Why not "would be 22 next week"? "Would have" is for unreal past" but this is the future "next week".

I heard a British native speaker say this.

Thank you.

Question

"She would have been 22 next week"?
If she were/was alive, she would have been 22 next week.

Why not "would be 22 next week"? "Would have" is for unreal past" but this is the future "next week".

I heard a British native speaker say this.

Thank you.

Answer

It's natural and correct.

Answer

Since the person being referred to is dead. She can no longer be 22 next week (get any older).
Also, since she is dead, she would have been (in the sense that it cannot be acheived  anymore now). 
You have to use "would have" to show  something could have happened, but for some reason cannot anymore.  Other examples are: I would have hit her right then,  I would have called her tomorrow. I would have taken the class next semester.  The topic has been referred to in some way previously in the conversation.