In Captain America: The Winter Soldier, when Natasha and Captain America meet what's left of Arnim Zola in the bunker at Camp Lehigh, he addresses Natasha as:
Dr. Arnim Zola: Rogers, Steven. Born, 1918. Romanoff, Natalia Alianovna. Born, 1984. [they see an old camera moving above them as it analyzes them]
Natasha Romanoff: It's some kind of a recording.
Dr. Arnim Zola: I am not a recording, Fräulein [...]
Captain America: The Winter Soldier
And in Avengers: Endgame, when Clint and Natasha arrive at Vormir, we see Red Skull address Black Widow as:
Red Skull: Welcome.
[Natasha and Clint draws their weapons]
Red Skull: Natasha, daughter of Ivan. Clint, son of Edith.
Natasha: Who are you? [...]
As far as I know, Ivan couldn't have been a nickname for Alianovna (e.g., Bob for Robert or Bill for William etc.). And as I found here, Alianovna is not specified to be a female or a male name.
So, is this an inconsistency on the part of the writers of the movies? Or is there any official/unofficial source that tells us why the her middle name was differently mentioned in the two films?
PS: Zola's mind was transferred into a complex computer system and he possessed knowledge that no one knew (as seen in Captain America: The Winter Soldier). Also, Cosmic Red Skull seemed to possess the information about everyone who visited Vormir (in Avengers: Infinity War and Avengers: Endgame as well). So, I assume that both of them knew what they were talking about.