[Gideon7]

It looks like many of her ‘corrections’ are simply differences of opinion on grammar or word usage, particularly regarding the capitalization of nouns. For example, Trump had capitalized the word “Nation”, which IMHO is perfectedly acceptable usage. In context the Nation is clearly a proper noun not a common noun. Ditto “States” and “Federal Government”.

I would say that most of her other corrections are similarly spurious.

[Gideon7]

Oops, that was *her* letter, haha. Nervermind.

[AndyJackson]

are simply differences of opinion on grammar or word usage

And many are simple ignorance. For instance we capitalized proper names. Titles are proper names when they are the referent to a specific individual who is known by that title. You might say I am president of my PTA since no one calls you exclusively President in that position. But President is the name of a specific person - DJT - properly called by this title and not by some other proper name, say, Trump, or Don. It's like the crown, a thing worn by the Queen and the Crown, the proper noun denoting the Queen in her capacity as head of state.

[jjotto]

The White House almost certainly has a style book and the same 'mistakes' show up in past White House letters.

Photo of a letter from Obama where he capitalizes 'Nation'.