Just a smidgen of fabrication to cast doubt on other, legitimate evidence.

Have you seen anything credible that supports what that now deleted tweet claimed?

On edit:
Is there a particular reason that we should consider Snopes untrustworthy?

I have seen a couple of posts recently indicating that Snopes was not giving the correct info.

I certainly don't think that Snopes is infallible and would be interested in any documented, uncorrected failures on their part.

That said, I still think they're far, far more credible than some of the posts we see here based on nothing but something that somebody or some bot announced on Twitter. Judging by the amount of recs some of them garner, some folks seem to only consider whether the twitter post is salacious or something they'd like to believe, with no consideration of the source or it's credibility. That's not directed at you personally, by the way.

On edit:
Regarding this particular instance, it's possible that the claim is true and if I see anything credible that supports it, I'll post that, too. Even Snopes said that they're waiting for a response from the tweeter with more info.

Claimes that Ashley Biden's diary is authentic, even though Ashley told the judge her diary was stolen and manipulated to defame her and lob FALSE accusations at the people she loves.

Change of ownership.

I don't have time right now to do a deep dive, but after a very brief perusal, I'm not seeing any conflict between the Snope's article and her letter. Snopes confirmed the existence of her diary, based on Ashley's statement. They aren't confirming anyone's misinterpretations or misrepresentations of the diary.

NYT article:
https://www.nytimes.com/2024/04/09/us/politics/project-veritas-ashley-biden-diary.html

Statement (pdf):
https://static01.nyt.com/newsgraphics/documenttools/654c5f7182bca1ee/6fe57478-full.pdf

Snopes article:
https://www.snopes.com/fact-check/ashley-biden-diary-claims/

It implies that it's real and right wingers use it to "prove" it's real.

They are no longer neutral. They posted Covid lies and misinformation as well. The ownership changed a few years ago.