Avengers 83 isn't the first appearance of a character, just the first published depiction of a character's likeness - as portrayed by an impostor. You might as well just go full Ween.
Really now, you haven't even read the issues you're discussing, have you?
In all 3 of the first appearances, the Enchantress is the one to give the Valkyrie's likeness/personality/powers to each character. In Avengers 83 she used the likeness on herself against the Avengers. In Hulk 142, she used the likeness on Samantha Pennington to attack the Hulk. In Defenders #4, she again used it on Barbara Norriss to help her with the Defenders.
What in the world is the difference?
Avengers 83:
1st time Valkyrie's name is used? Check.
First Valkyrie's likeness? Check.
Prominent cover appearance? Check.
Valkyrie's looks exactly the same as in every appearance over the next 30-40 years? Check.
The same would be true then with 1st SA appearance of Captain America in Strange Tales 114..
Strange Tales 114:
1st time Cap's name is used in the Silver Age? Check.
First Cap's likeness? Check.
Prominent cover appearance? Check.
Cap's looks exactly the same as in every appearance over the next 30-40 years? Check
First appearance and "first SA appearance" are not the same thing? Check.
-J.
Actually I do consider ST 114 as the 1st SA Cap appearance. Point being?
Everyone already knew (or should have known) who captain America was when they "brought him back" in the SA. There was therefore context to the "imposter appearance" in ST 114.
The same cannot be said for Valkyrie which was actually a first appearance of the character, irrespective of the subsequent ret-con.
-J.
It does not matter. If there was a Valkyrie appearance in the Golden Age, we would have the same discussion except to discuss which comic is the first SA appearance of Valkyrie, same as Cap in ST 114 vs Avengers 4